feat(restheadspec): ✨ Add custom SQL JOIN support

- Introduced `x-custom-sql-join` header for custom SQL JOIN clauses.
- Supports single and multiple JOINs, separated by `|`.
- Enhanced query handling to apply custom JOINs directly.
- Updated documentation to reflect new functionality.
- Added tests for parsing custom SQL JOINs from query parameters and headers.

go.mod

@@ -116,7 +116,6 @@ require (
 	github.com/shirou/gopsutil/v4 v4.25.6 // indirect
 	github.com/shopspring/decimal v1.4.0 // indirect
 	github.com/sirupsen/logrus v1.9.3 // indirect
-	github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 // indirect
 	github.com/spf13/afero v1.15.0 // indirect
 	github.com/spf13/cast v1.10.0 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect

go.sum

@@ -88,8 +88,6 @@ github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S
 github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 github.com/getsentry/sentry-go v0.40.0 h1:VTJMN9zbTvqDqPwheRVLcp0qcUcM+8eFivvGocAaSbo=
 github.com/getsentry/sentry-go v0.40.0/go.mod h1:eRXCoh3uvmjQLY6qu63BjUZnaBu5L5WhMV1RwYO8W5s=
-github.com/glebarez/go-sqlite v1.21.2 h1:3a6LFC4sKahUunAmynQKLZceZCOzUthkRkEAl9gAXWo=
-github.com/glebarez/go-sqlite v1.21.2/go.mod h1:sfxdZyhQjTM2Wry3gVYWaW072Ri1WMdWJi0k6+3382k=
 github.com/glebarez/go-sqlite v1.22.0 h1:uAcMJhaA6r3LHMTFgP0SifzgXg46yJkgxqyuyec+ruQ=
 github.com/glebarez/go-sqlite v1.22.0/go.mod h1:PlBIdHe0+aUEFn+r2/uthrWq4FxbzugL0L8Li6yQJbc=
 github.com/glebarez/sqlite v1.11.0 h1:wSG0irqzP6VurnMEpFGer5Li19RpIRi2qvQz++w0GMw=
@@ -107,17 +105,15 @@ github.com/go-viper/mapstructure/v2 v2.4.0 h1:EBsztssimR/CONLSZZ04E8qAkxNYq4Qp9L
 github.com/go-viper/mapstructure/v2 v2.4.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/golang-jwt/jwt/v5 v5.0.0/go.mod h1:pqrtFR0X4osieyHYxtmOUWsAWrfe1Q5UVIyoH402zdk=
 github.com/golang-jwt/jwt/v5 v5.2.1/go.mod h1:pqrtFR0X4osieyHYxtmOUWsAWrfe1Q5UVIyoH402zdk=
-github.com/golang-jwt/jwt/v5 v5.2.2 h1:Rl4B7itRWVtYIHFrSNd7vhTiz9UpLdi6gZhZ3wEeDy8=
 github.com/golang-jwt/jwt/v5 v5.2.2/go.mod h1:pqrtFR0X4osieyHYxtmOUWsAWrfe1Q5UVIyoH402zdk=
 github.com/golang-jwt/jwt/v5 v5.3.0 h1:pv4AsKCKKZuqlgs5sUmn4x8UlGa0kEVt/puTpKx9vvo=
+github.com/golang-jwt/jwt/v5 v5.3.0/go.mod h1:fxCRLWMO43lRc8nhHWY6LGqRcf+1gQWArsqaEUEa5bE=
 github.com/golang-sql/civil v0.0.0-20220223132316-b832511892a9 h1:au07oEsX2xN0ktxqI+Sida1w446QrXBRJ0nee3SNZlA=
 github.com/golang-sql/civil v0.0.0-20220223132316-b832511892a9/go.mod h1:8vg3r2VgvsThLBIFL93Qb5yWzgyZWhEmBwUJWevAkK0=
 github.com/golang-sql/sqlexp v0.1.0 h1:ZCD6MBpcuOVfGVqsEmY5/4FtYiKz6tSyUv9LPEDei6A=
 github.com/golang-sql/sqlexp v0.1.0/go.mod h1:J4ad9Vo8ZCWQ2GMrC4UCQy1JpCbwU9m3EOqtpKwwwHI=
 github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
 github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
-github.com/golang/snappy v0.0.4 h1:yAGX7huGHXlcLOEtBnF4w7FQwA26wojNCwOYAEhLjQM=
-github.com/golang/snappy v0.0.4/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/golang/snappy v1.0.0 h1:Oy607GVXHs7RtbggtPBnr2RmDArIsAefDwvrdWvRhGs=
 github.com/golang/snappy v1.0.0/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/google/go-cmp v0.5.6/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
@@ -145,8 +141,6 @@ github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsI
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
 github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
 github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
-github.com/jackc/pgx/v5 v5.6.0 h1:SWJzexBzPL5jb0GEsrPMLIsi/3jOo7RHlzTjcAeDrPY=
-github.com/jackc/pgx/v5 v5.6.0/go.mod h1:DNZ/vlrUnhWCoFGxHAG8U2ljioxukquj7utPDgtQdTw=
 github.com/jackc/pgx/v5 v5.8.0 h1:TYPDoleBBme0xGSAX3/+NujXXtpZn9HBONkQC7IEZSo=
 github.com/jackc/pgx/v5 v5.8.0/go.mod h1:QVeDInX2m9VyzvNeiCJVjCkNFqzsNb43204HshNSZKw=
 github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
@@ -164,8 +158,6 @@ github.com/jinzhu/inflection v1.0.0/go.mod h1:h+uFLlag+Qp1Va5pdKtLDYj+kHp5pxUVkr
 github.com/jinzhu/now v1.1.5 h1:/o9tlHleP7gOFmsnYNz3RGnqzefHA47wQpKrrdTIwXQ=
 github.com/jinzhu/now v1.1.5/go.mod h1:d3SSVoowX0Lcu0IBviAWJpolVfI5UJVZZ7cO71lE/z8=
 github.com/kisielk/sqlstruct v0.0.0-20201105191214-5f3e10d3ab46/go.mod h1:yyMNCyc/Ib3bDTKd379tNMpB/7/H5TjM2Y9QJ5THLbE=
-github.com/klauspost/compress v1.18.0 h1:c/Cqfb0r+Yi+JtIEq73FWXVkRonBlf0CRNYc8Zttxdo=
-github.com/klauspost/compress v1.18.0/go.mod h1:2Pp+KzxcywXVXMr50+X0Q/Lsb43OQHYWRCY2AiWywWQ=
 github.com/klauspost/compress v1.18.2 h1:iiPHWW0YrcFgpBYhsA6D1+fqHssJscY/Tm/y2Uqnapk=
 github.com/klauspost/compress v1.18.2/go.mod h1:R0h/fSBs8DE4ENlcrlib3PsXS61voFxhIs2DeRhCvJ4=
 github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
@@ -183,8 +175,6 @@ github.com/magiconair/properties v1.8.10 h1:s31yESBquKXCV9a/ScB3ESkOjUYYv+X0rg8S
 github.com/magiconair/properties v1.8.10/go.mod h1:Dhd985XPs7jluiymwWYZ0G4Z61jb3vdS329zhj2hYo0=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
-github.com/mattn/go-sqlite3 v1.14.32 h1:JD12Ag3oLy1zQA+BNn74xRgaBbdhbNIDYvQUEuuErjs=
-github.com/mattn/go-sqlite3 v1.14.32/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
 github.com/mattn/go-sqlite3 v1.14.33 h1:A5blZ5ulQo2AtayQ9/limgHEkFreKj1Dv226a1K73s0=
 github.com/mattn/go-sqlite3 v1.14.33/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
 github.com/microsoft/go-mssqldb v1.8.2/go.mod h1:vp38dT33FGfVotRiTmDo3bFyaHq+p3LektQrjTULowo=
@@ -246,18 +236,12 @@ github.com/prometheus/client_golang v1.23.2 h1:Je96obch5RDVy3FDMndoUsjAhG5Edi49h
 github.com/prometheus/client_golang v1.23.2/go.mod h1:Tb1a6LWHB3/SPIzCoaDXI4I8UHKeFTEQ1YCr+0Gyqmg=
 github.com/prometheus/client_model v0.6.2 h1:oBsgwpGs7iVziMvrGhE53c/GrLUsZdHnqNwqPLxwZyk=
 github.com/prometheus/client_model v0.6.2/go.mod h1:y3m2F6Gdpfy6Ut/GBsUqTWZqCUvMVzSfMLjcu6wAwpE=
-github.com/prometheus/common v0.66.1 h1:h5E0h5/Y8niHc5DlaLlWLArTQI7tMrsfQjHV+d9ZoGs=
-github.com/prometheus/common v0.66.1/go.mod h1:gcaUsgf3KfRSwHY4dIMXLPV0K/Wg1oZ8+SbZk/HH/dA=
 github.com/prometheus/common v0.67.4 h1:yR3NqWO1/UyO1w2PhUvXlGQs/PtFmoveVO0KZ4+Lvsc=
 github.com/prometheus/common v0.67.4/go.mod h1:gP0fq6YjjNCLssJCQp0yk4M8W6ikLURwkdd/YKtTbyI=
-github.com/prometheus/procfs v0.16.1 h1:hZ15bTNuirocR6u0JZ6BAHHmwS1p8B4P6MRqxtzMyRg=
-github.com/prometheus/procfs v0.16.1/go.mod h1:teAbpZRB1iIAJYREa1LsoWUXykVXA1KlTmWl8x/U+Is=
 github.com/prometheus/procfs v0.19.2 h1:zUMhqEW66Ex7OXIiDkll3tl9a1ZdilUOd/F6ZXw4Vws=
 github.com/prometheus/procfs v0.19.2/go.mod h1:M0aotyiemPhBCM0z5w87kL22CxfcH05ZpYlu+b4J7mw=
 github.com/puzpuzpuz/xsync/v3 v3.5.1 h1:GJYJZwO6IdxN/IKbneznS6yPkVC+c3zyY/j19c++5Fg=
 github.com/puzpuzpuz/xsync/v3 v3.5.1/go.mod h1:VjzYrABPabuM4KyBh1Ftq6u8nhwY5tBPKP9jpmh0nnA=
-github.com/redis/go-redis/v9 v9.17.1 h1:7tl732FjYPRT9H9aNfyTwKg9iTETjWjGKEJ2t/5iWTs=
-github.com/redis/go-redis/v9 v9.17.1/go.mod h1:u410H11HMLoB+TP67dz8rL9s6QW2j76l0//kSOd3370=
 github.com/redis/go-redis/v9 v9.17.2 h1:P2EGsA4qVIM3Pp+aPocCJ7DguDHhqrXNhVcEp4ViluI=
 github.com/redis/go-redis/v9 v9.17.2/go.mod h1:u410H11HMLoB+TP67dz8rL9s6QW2j76l0//kSOd3370=
 github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec h1:W09IVJc94icq4NjY3clb7Lk8O1qJ8BdBEF8z0ibU0rE=
@@ -268,8 +252,6 @@ github.com/rogpeppe/go-internal v1.13.1 h1:KvO1DLK/DRN07sQ1LQKScxyZJuNnedQ5/wKSR
 github.com/rogpeppe/go-internal v1.13.1/go.mod h1:uMEvuHeurkdAXX61udpOXGD/AzZDWNMNyH2VO9fmH0o=
 github.com/rs/xid v1.4.0 h1:qd7wPTDkN6KQx2VmMBLrpHkiyQwgFXRnkOLacUiaSNY=
 github.com/rs/xid v1.4.0/go.mod h1:trrq9SKmegXys3aeAKXMUTdJsYXVwGY3RLcfgqegfbg=
-github.com/sagikazarmark/locafero v0.11.0 h1:1iurJgmM9G3PA/I+wWYIOw/5SyBtxapeHDcg+AAIFXc=
-github.com/sagikazarmark/locafero v0.11.0/go.mod h1:nVIGvgyzw595SUSUE6tvCp3YYTeHs15MvlmU87WwIik=
 github.com/sagikazarmark/locafero v0.12.0 h1:/NQhBAkUb4+fH1jivKHWusDYFjMOOKU88eegjfxfHb4=
 github.com/sagikazarmark/locafero v0.12.0/go.mod h1:sZh36u/YSZ918v0Io+U9ogLYQJ9tLLBmM4eneO6WwsI=
 github.com/shirou/gopsutil/v4 v4.25.6 h1:kLysI2JsKorfaFPcYmcJqbzROzsBWEOAtw6A7dIfqXs=
@@ -278,8 +260,6 @@ github.com/shopspring/decimal v1.4.0 h1:bxl37RwXBklmTi0C79JfXCEBD1cqqHt0bbgBAGFp
 github.com/shopspring/decimal v1.4.0/go.mod h1:gawqmDU56v4yIKSwfBSFip1HdCCXN8/+DMd9qYNcwME=
 github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
 github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
-github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 h1:+jumHNA0Wrelhe64i8F6HNlS8pkoyMv5sreGx2Ry5Rw=
-github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8/go.mod h1:3n1Cwaq1E1/1lhQhtRK2ts/ZwZEhjcQeJQ1RuC6Q/8U=
 github.com/spf13/afero v1.15.0 h1:b/YBCLWAJdFWJTN9cLhiXXcD7mzKn9Dm86dNnfyQw1I=
 github.com/spf13/afero v1.15.0/go.mod h1:NC2ByUVxtQs4b3sIUphxK0NioZnmxgyCrfzeuq8lxMg=
 github.com/spf13/cast v1.10.0 h1:h2x0u2shc1QuLHfxi+cTJvs30+ZAHOGRic8uyGTDWxY=
@@ -310,11 +290,9 @@ github.com/testcontainers/testcontainers-go v0.40.0/go.mod h1:FSXV5KQtX2HAMlm7U3
 github.com/tidwall/gjson v1.14.2/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
 github.com/tidwall/gjson v1.18.0 h1:FIDeeyB800efLX89e5a8Y0BNH+LOngJyGrIWxG2FKQY=
 github.com/tidwall/gjson v1.18.0/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
-github.com/tidwall/match v1.1.1 h1:+Ho715JplO36QYgwN9PGYNhgZvoUSc9X2c80KVTi+GA=
 github.com/tidwall/match v1.1.1/go.mod h1:eRSPERbgtNPcGhD8UCthc6PmLEQXEWd3PRB5JTxsfmM=
 github.com/tidwall/match v1.2.0 h1:0pt8FlkOwjN2fPt4bIl4BoNxb98gGHN2ObFEDkrfZnM=
 github.com/tidwall/match v1.2.0/go.mod h1:eRSPERbgtNPcGhD8UCthc6PmLEQXEWd3PRB5JTxsfmM=
-github.com/tidwall/pretty v1.2.0 h1:RWIZEg2iJ8/g6fDDYzMpobmaoGh5OLl4AXtGUGPcqCs=
 github.com/tidwall/pretty v1.2.0/go.mod h1:ITEVvHYasfjBbM0u2Pg8T2nJnzm8xPwvNhhsoaGGjNU=
 github.com/tidwall/pretty v1.2.1 h1:qjsOFOWWQl+N3RsoF5/ssm1pHmJJwhjlSbZ51I6wMl4=
 github.com/tidwall/pretty v1.2.1/go.mod h1:ITEVvHYasfjBbM0u2Pg8T2nJnzm8xPwvNhhsoaGGjNU=
@@ -344,8 +322,6 @@ github.com/warkanum/bun v1.2.17 h1:HP8eTuKSNcqMDhhIPFxEbgV/yct6RR0/c3qHH3PNZUA=
 github.com/warkanum/bun v1.2.17/go.mod h1:jMoNg2n56ckaawi/O/J92BHaECmrz6IRjuMWqlMaMTM=
 github.com/xdg-go/pbkdf2 v1.0.0 h1:Su7DPu48wXMwC3bs7MCNG+z4FhcyEuz5dlvchbq0B0c=
 github.com/xdg-go/pbkdf2 v1.0.0/go.mod h1:jrpuAogTd400dnrH08LKmI/xc1MbPOebTwRqcT5RDeI=
-github.com/xdg-go/scram v1.1.2 h1:FHX5I5B4i4hKRVRBCFRxq1iQRej7WO3hhBuJf+UUySY=
-github.com/xdg-go/scram v1.1.2/go.mod h1:RT/sEzTbU5y00aCK8UOx6R7YryM0iF1N2MOmC3kKLN4=
 github.com/xdg-go/scram v1.2.0 h1:bYKF2AEwG5rqd1BumT4gAnvwU/M9nBp2pTSxeZw7Wvs=
 github.com/xdg-go/scram v1.2.0/go.mod h1:3dlrS0iBaWKYVt2ZfA4cj48umJZ+cAEbR6/SjLA88I8=
 github.com/xdg-go/stringprep v1.0.4 h1:XLI/Ng3O1Atzq0oBs3TWm+5ZVgkq2aqdlvP9JtoZ6c8=
@@ -381,16 +357,10 @@ go.opentelemetry.io/proto/otlp v1.7.1 h1:gTOMpGDb0WTBOP8JaO72iL3auEZhVmAQg4ipjOV
 go.opentelemetry.io/proto/otlp v1.7.1/go.mod h1:b2rVh6rfI/s2pHWNlB7ILJcRALpcNDzKhACevjI+ZnE=
 go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
-go.uber.org/multierr v1.10.0 h1:S0h4aNzvfcFsC3dRF1jLoaov7oRaKqRGC/pUEJ2yvPQ=
-go.uber.org/multierr v1.10.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
 go.uber.org/multierr v1.11.0 h1:blXXJkSxSSfBVBlC76pxqeO+LN3aDfLQo+309xJstO0=
 go.uber.org/multierr v1.11.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
-go.uber.org/zap v1.27.0 h1:aJMhYGrd5QSmlpLMr2MftRKl7t8J8PTZPA732ud/XR8=
-go.uber.org/zap v1.27.0/go.mod h1:GB2qFLM7cTU87MWRP2mPIjqfIDnGu+VIO4V/SdhGo2E=
 go.uber.org/zap v1.27.1 h1:08RqriUEv8+ArZRYSTXy1LeBScaMpVSTBhCeaZYfMYc=
 go.uber.org/zap v1.27.1/go.mod h1:GB2qFLM7cTU87MWRP2mPIjqfIDnGu+VIO4V/SdhGo2E=
-go.yaml.in/yaml/v2 v2.4.2 h1:DzmwEr2rDGHl7lsFgAHxmNz/1NlQ7xLIrlN2h5d1eGI=
-go.yaml.in/yaml/v2 v2.4.2/go.mod h1:081UH+NErpNdqlCXm3TtEran0rJZGxAYx9hb/ELlsPU=
 go.yaml.in/yaml/v2 v2.4.3 h1:6gvOSjQoTB3vt1l+CU+tSyi/HOjfOjRLJ4YwYZGwRO0=
 go.yaml.in/yaml/v2 v2.4.3/go.mod h1:zSxWcmIDjOzPXpjlTTbAsKokqkDNAVtZO0WOMiT90s8=
 go.yaml.in/yaml/v3 v3.0.4 h1:tfq32ie2Jv2UxXFdLJdh3jXuOzWiL1fo0bu/FbuKpbc=
@@ -407,12 +377,8 @@ golang.org/x/crypto v0.21.0/go.mod h1:0BP7YvVV9gBbVKyeTG0Gyn+gZm94bibOW5BjDEYAOM
 golang.org/x/crypto v0.22.0/go.mod h1:vr6Su+7cTlO45qkww3VDJlzDn0ctJvRgYbC2NvXHt+M=
 golang.org/x/crypto v0.23.0/go.mod h1:CKFgDieR+mRhux2Lsu27y0fO304Db0wZe70UKqHu0v8=
 golang.org/x/crypto v0.24.0/go.mod h1:Z1PMYSOR5nyMcyAVAIQSKCDwalqy85Aqn1x3Ws4L5DM=
-golang.org/x/crypto v0.43.0 h1:dduJYIi3A3KOfdGOHX8AVZ/jGiyPa3IbBozJ5kNuE04=
-golang.org/x/crypto v0.43.0/go.mod h1:BFbav4mRNlXJL4wNeejLpWxB7wMbc79PdRGhWKncxR0=
 golang.org/x/crypto v0.46.0 h1:cKRW/pmt1pKAfetfu+RCEvjvZkA9RimPbh7bhFjGVBU=
 golang.org/x/crypto v0.46.0/go.mod h1:Evb/oLKmMraqjZ2iQTwDwvCtJkczlDuTmdJXoZVzqU0=
-golang.org/x/exp v0.0.0-20251113190631-e25ba8c21ef6 h1:zfMcR1Cs4KNuomFFgGefv5N0czO2XZpUbxGUy8i8ug0=
-golang.org/x/exp v0.0.0-20251113190631-e25ba8c21ef6/go.mod h1:46edojNIoXTNOhySWIWdix628clX9ODXwPsQuG6hsK0=
 golang.org/x/exp v0.0.0-20251219203646-944ab1f22d93 h1:fQsdNF2N+/YewlRZiricy4P1iimyPKZ/xwniHj8Q2a0=
 golang.org/x/exp v0.0.0-20251219203646-944ab1f22d93/go.mod h1:EPRbTFwzwjXj9NpYyyrvenVh9Y+GFeEvMNh7Xuz7xgU=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
@@ -421,8 +387,6 @@ golang.org/x/mod v0.9.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/mod v0.12.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/mod v0.15.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/mod v0.17.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
-golang.org/x/mod v0.30.0 h1:fDEXFVZ/fmCKProc/yAXXUijritrDzahmwwefnjoPFk=
-golang.org/x/mod v0.30.0/go.mod h1:lAsf5O2EvJeSFMiBxXDki7sCgAxEUcZHXoXMKT4GJKc=
 golang.org/x/mod v0.31.0 h1:HaW9xtz0+kOcWKwli0ZXy79Ix+UW/vOfmWI5QVd2tgI=
 golang.org/x/mod v0.31.0/go.mod h1:43JraMp9cGx1Rx3AqioxrbrhNsLl2l/iNAvuBkrezpg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
@@ -442,8 +406,6 @@ golang.org/x/net v0.22.0/go.mod h1:JKghWKKOSdJwpW2GEx0Ja7fmaKnMsbu+MWVZTokSYmg=
 golang.org/x/net v0.24.0/go.mod h1:2Q7sJY5mzlzWjKtYUEXSlBWCdyaioyXzRB2RtU8KVE8=
 golang.org/x/net v0.25.0/go.mod h1:JkAGAh7GEvH74S6FOH42FLoXpXbE/aqXSrIQjXgsiwM=
 golang.org/x/net v0.26.0/go.mod h1:5YKkiSynbBIh3p6iOc/vibscux0x38BZDkn8sCUPxHE=
-golang.org/x/net v0.45.0 h1:RLBg5JKixCy82FtLJpeNlVM0nrSqpCRYzVU1n8kj0tM=
-golang.org/x/net v0.45.0/go.mod h1:ECOoLqd5U3Lhyeyo/QDCEVQ4sNgYsqvCZ722XogGieY=
 golang.org/x/net v0.48.0 h1:zyQRTTrjc33Lhh0fBgT/H3oZq9WuvRR5gPC70xpDiQU=
 golang.org/x/net v0.48.0/go.mod h1:+ndRgGjkh8FGtu1w1FGbEC31if4VrNVMuKTgcAAnQRY=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -453,8 +415,6 @@ golang.org/x/sync v0.3.0/go.mod h1:FU7BRWz2tNW+3quACPkgCx/L+uEAv1htQ0V83Z9Rj+Y=
 golang.org/x/sync v0.6.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sync v0.9.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sync v0.18.0 h1:kr88TuHDroi+UVf+0hZnirlk8o8T+4MrK6mr60WkH/I=
-golang.org/x/sync v0.18.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
 golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -480,8 +440,6 @@ golang.org/x/sys v0.18.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.19.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.20.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
-golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
 golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/telemetry v0.0.0-20240228155512-f48c80bd79b2/go.mod h1:TeRTkGYfJXctD9OcfyVLyj2J3IxLnKwHJR8f4D8a3YE=
@@ -499,9 +457,8 @@ golang.org/x/term v0.18.0/go.mod h1:ILwASektA3OnRv7amZ1xhE/KTR+u50pbXfZ03+6Nx58=
 golang.org/x/term v0.19.0/go.mod h1:2CuTdWZ7KHSQwUzKva0cbMg6q2DMI3Mmxp+gKJbskEk=
 golang.org/x/term v0.20.0/go.mod h1:8UkIAJTvZgivsXaD6/pH6U9ecQzZ45awqEOzuCvwpFY=
 golang.org/x/term v0.21.0/go.mod h1:ooXLefLobQVslOqselCNF4SxFAaoS6KujMbsGzSDmX0=
-golang.org/x/term v0.36.0 h1:zMPR+aF8gfksFprF/Nc/rd1wRS1EI6nDBGyWAvDzx2Q=
-golang.org/x/term v0.36.0/go.mod h1:Qu394IJq6V6dCBRgwqshf3mPF85AqzYEzofzRdZkWss=
 golang.org/x/term v0.38.0 h1:PQ5pkm/rLO6HnxFR7N2lJHOZX6Kez5Y1gDSJla6jo7Q=
+golang.org/x/term v0.38.0/go.mod h1:bSEAKrOT1W+VSu9TSCMtoGEOUcKxOKgl3LE5QEF/xVg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
@@ -516,8 +473,6 @@ golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/text v0.15.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=
 golang.org/x/text v0.20.0/go.mod h1:D4IsuqiFMhST5bX19pQ9ikHC2GsaKyk/oF+pn3ducp4=
-golang.org/x/text v0.30.0 h1:yznKA/E9zq54KzlzBEAWn1NXSQ8DIp/NYMy88xJjl4k=
-golang.org/x/text v0.30.0/go.mod h1:yDdHFIX9t+tORqspjENWgzaCVXgk0yYnYuSZ8UzzBVM=
 golang.org/x/text v0.32.0 h1:ZD01bjUt1FQ9WJ0ClOL5vxgxOI/sVCNgX1YtKwcY0mU=
 golang.org/x/text v0.32.0/go.mod h1:o/rUWzghvpD5TXrTIBuJU77MTaN0ljMWE47kxGJQ7jY=
 golang.org/x/time v0.14.0 h1:MRx4UaLrDotUKUdCIqzPC48t1Y9hANFKIRpNx+Te8PI=
@@ -528,9 +483,8 @@ golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/tools v0.13.0/go.mod h1:HvlwmtVNQAhOuCjW7xxvovg8wbNq7LwfXh/k7wXUl58=
 golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d/go.mod h1:aiJjzUbINMkxbQROHiO6hDPo2LHcIPhhQsa9DLh0yGk=
-golang.org/x/tools v0.39.0 h1:ik4ho21kwuQln40uelmciQPp9SipgNDdrafrYA4TmQQ=
-golang.org/x/tools v0.39.0/go.mod h1:JnefbkDPyD8UU2kI5fuf8ZX4/yUeh9W877ZeBONxUqQ=
 golang.org/x/tools v0.40.0 h1:yLkxfA+Qnul4cs9QA3KnlFu0lVmd8JJfoq+E41uSutA=
+golang.org/x/tools v0.40.0/go.mod h1:Ik/tzLRlbscWpqqMRjyWYDisX8bG13FrdXp3o4Sr9lc=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gonum.org/v1/gonum v0.16.0 h1:5+ul4Swaf3ESvrOnidPp4GZbzf0mxVQpDCYUQE7OJfk=
@@ -541,8 +495,6 @@ google.golang.org/genproto/googleapis/rpc v0.0.0-20250825161204-c5933d9347a5 h1:
 google.golang.org/genproto/googleapis/rpc v0.0.0-20250825161204-c5933d9347a5/go.mod h1:M4/wBTSeyLxupu3W3tJtOgB14jILAS/XWPSSa3TAlJc=
 google.golang.org/grpc v1.75.0 h1:+TW+dqTd2Biwe6KKfhE5JpiYIBWq865PhKGSXiivqt4=
 google.golang.org/grpc v1.75.0/go.mod h1:JtPAzKiq4v1xcAB2hydNlWI2RnF85XXcV0mhKXr2ecQ=
-google.golang.org/protobuf v1.36.8 h1:xHScyCOEuuwZEc6UtSOvPbAT4zRh0xcNRYekJwfqyMc=
-google.golang.org/protobuf v1.36.8/go.mod h1:fuxRtAxBytpl4zzqUh6/eyUujkJdNiuEkXntxiD/uRU=
 google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
 google.golang.org/protobuf v1.36.11/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
@@ -561,7 +513,6 @@ gorm.io/driver/sqlite v1.6.0 h1:WHRRrIiulaPiPFmDcod6prc4l2VGVWHz80KspNsxSfQ=
 gorm.io/driver/sqlite v1.6.0/go.mod h1:AO9V1qIQddBESngQUKWL9yoH93HIeA1X6V633rBwyT8=
 gorm.io/driver/sqlserver v1.6.3 h1:UR+nWCuphPnq7UxnL57PSrlYjuvs+sf1N59GgFX7uAI=
 gorm.io/driver/sqlserver v1.6.3/go.mod h1:VZeNn7hqX1aXoN5TPAFGWvxWG90xtA8erGn2gQmpc6U=
-gorm.io/gorm v1.30.0 h1:qbT5aPv1UH8gI99OsRlvDToLxW5zR7FzS9acZDOZcgs=
 gorm.io/gorm v1.30.0/go.mod h1:8Z33v652h4//uMA76KjeDH8mJXPm1QNCYrMeatR0DOE=
 gorm.io/gorm v1.31.1 h1:7CA8FTFz/gRfgqgpeKIBcervUn3xSyPUmr6B2WXJ7kg=
 gorm.io/gorm v1.31.1/go.mod h1:XyQVbO2k6YkOis7C2437jSit3SsDK72s7n7rsSHd+Gs=
@@ -579,8 +530,6 @@ modernc.org/gc/v3 v3.1.1 h1:k8T3gkXWY9sEiytKhcgyiZ2L0DTyCQ/nvX+LoCljoRE=
 modernc.org/gc/v3 v3.1.1/go.mod h1:HFK/6AGESC7Ex+EZJhJ2Gni6cTaYpSMmU/cT9RmlfYY=
 modernc.org/goabi0 v0.2.0 h1:HvEowk7LxcPd0eq6mVOAEMai46V+i7Jrj13t4AzuNks=
 modernc.org/goabi0 v0.2.0/go.mod h1:CEFRnnJhKvWT1c1JTI3Avm+tgOWbkOu5oPA8eH8LnMI=
-modernc.org/libc v1.67.0 h1:QzL4IrKab2OFmxA3/vRYl0tLXrIamwrhD6CKD4WBVjQ=
-modernc.org/libc v1.67.0/go.mod h1:QvvnnJ5P7aitu0ReNpVIEyesuhmDLQ8kaEoyMjIFZJA=
 modernc.org/libc v1.67.4 h1:zZGmCMUVPORtKv95c2ReQN5VDjvkoRm9GWPTEPuvlWg=
 modernc.org/libc v1.67.4/go.mod h1:QvvnnJ5P7aitu0ReNpVIEyesuhmDLQ8kaEoyMjIFZJA=
 modernc.org/mathutil v1.7.1 h1:GCZVGXdaN8gTqB1Mf/usp1Y/hSqgI2vAGGP4jZMCxOU=
@@ -591,8 +540,6 @@ modernc.org/opt v0.1.4 h1:2kNGMRiUjrp4LcaPuLY2PzUfqM/w9N23quVwhKt5Qm8=
 modernc.org/opt v0.1.4/go.mod h1:03fq9lsNfvkYSfxrfUhZCWPk1lm4cq4N+Bh//bEtgns=
 modernc.org/sortutil v1.2.1 h1:+xyoGf15mM3NMlPDnFqrteY07klSFxLElE2PVuWIJ7w=
 modernc.org/sortutil v1.2.1/go.mod h1:7ZI3a3REbai7gzCLcotuw9AC4VZVpYMjDzETGsSMqJE=
-modernc.org/sqlite v1.40.1 h1:VfuXcxcUWWKRBuP8+BR9L7VnmusMgBNNnBYGEe9w/iY=
-modernc.org/sqlite v1.40.1/go.mod h1:9fjQZ0mB1LLP0GYrp39oOJXx/I2sxEnZtzCmEQIKvGE=
 modernc.org/sqlite v1.42.2 h1:7hkZUNJvJFN2PgfUdjni9Kbvd4ef4mNLOu0B9FGxM74=
 modernc.org/sqlite v1.42.2/go.mod h1:+VkC6v3pLOAE0A0uVucQEcbVW0I5nHCeDaBf+DpsQT8=
 modernc.org/strutil v1.2.1 h1:UneZBkQA+DX2Rp35KcM69cSsNES9ly8mQWD71HKlOA0=

pkg/common/adapters/database/bun.go

@@ -211,6 +211,7 @@ type BunSelectQuery struct {
 	deferredPreloads []deferredPreload // Preloads to execute as separate queries
 	inJoinContext    bool              // Track if we're in a JOIN relation context
 	joinTableAlias   string            // Alias to use for JOIN conditions
+	skipAutoDetect   bool              // Skip auto-detection to prevent circular calls
 }
 
 // deferredPreload represents a preload that will be executed as a separate query
@@ -531,22 +532,25 @@ func (b *BunSelectQuery) Preload(relation string, conditions ...interface{}) com
 func (b *BunSelectQuery) PreloadRelation(relation string, apply ...func(common.SelectQuery) common.SelectQuery) common.SelectQuery {
 	// Auto-detect relationship type and choose optimal loading strategy
 	// Get the model from the query if available
-	model := b.query.GetModel()
+	// Skip auto-detection if flag is set (prevents circular calls from JoinRelation)
-	if model != nil && model.Value() != nil {
+	if !b.skipAutoDetect {
-		relType := reflection.GetRelationType(model.Value(), relation)
+		model := b.query.GetModel()
+		if model != nil && model.Value() != nil {
+			relType := reflection.GetRelationType(model.Value(), relation)
 
-		// Log the detected relationship type
+			// Log the detected relationship type
-		logger.Debug("PreloadRelation '%s' detected as: %s", relation, relType)
+			logger.Debug("PreloadRelation '%s' detected as: %s", relation, relType)
 
-		// If this is a belongs-to or has-one relation, use JOIN for better performance
+			// If this is a belongs-to or has-one relation, use JOIN for better performance
-		if relType.ShouldUseJoin() {
+			if relType.ShouldUseJoin() {
-			logger.Info("Using JOIN strategy for %s relation '%s'", relType, relation)
+				logger.Info("Using JOIN strategy for %s relation '%s'", relType, relation)
-			return b.JoinRelation(relation, apply...)
+				return b.JoinRelation(relation, apply...)
-		}
+			}
 
-		// For has-many, many-to-many, or unknown: use separate query (safer default)
+			// For has-many, many-to-many, or unknown: use separate query (safer default)
-		if relType == reflection.RelationHasMany || relType == reflection.RelationManyToMany {
+			if relType == reflection.RelationHasMany || relType == reflection.RelationManyToMany {
-			logger.Debug("Using separate query for %s relation '%s'", relType, relation)
+				logger.Debug("Using separate query for %s relation '%s'", relType, relation)
+			}
 		}
 	}
 
@@ -559,7 +563,7 @@ func (b *BunSelectQuery) PreloadRelation(relation string, apply ...func(common.S
 	const safeAliasLimit = 35 // Leave room for column names
 
 	// If the alias chain is too long, defer this preload to be executed as a separate query
-	if len(aliasChain) > safeAliasLimit {
+	if len(relationParts) > 1 && len(aliasChain) > safeAliasLimit {
 		logger.Info("Preload relation '%s' creates long alias chain '%s' (%d chars). "+
 			"Using separate query to avoid PostgreSQL %d-char identifier limit.",
 			relation, aliasChain, len(aliasChain), postgresIdentifierLimit)
@@ -683,6 +687,10 @@ func (b *BunSelectQuery) JoinRelation(relation string, apply ...func(common.Sele
 
 	// Use PreloadRelation with the wrapped functions
 	// Bun's Relation() will use JOIN for belongs-to and has-one relations
+	// CRITICAL: Set skipAutoDetect flag to prevent circular call
+	// (PreloadRelation would detect belongs-to and call JoinRelation again)
+	b.skipAutoDetect = true
+	defer func() { b.skipAutoDetect = false }()
 	return b.PreloadRelation(relation, wrappedApply...)
 }
 
@@ -742,6 +750,8 @@ func (b *BunSelectQuery) Scan(ctx context.Context, dest interface{}) (err error)
 			logger.Warn("Failed to execute deferred preloads: %v", err)
 			// Don't fail the whole query, just log the warning
 		}
+		// Clear deferred preloads to prevent re-execution
+		b.deferredPreloads = nil
 	}
 
 	return nil
@@ -810,6 +820,8 @@ func (b *BunSelectQuery) ScanModel(ctx context.Context) (err error) {
 			logger.Warn("Failed to execute deferred preloads: %v", err)
 			// Don't fail the whole query, just log the warning
 		}
+		// Clear deferred preloads to prevent re-execution
+		b.deferredPreloads = nil
 	}
 
 	return nil
@@ -898,13 +910,30 @@ func (b *BunSelectQuery) loadChildRelationForRecord(ctx context.Context, record
 		return nil
 	}
 
-	// Get the interface value to pass to Bun
+	// Get a pointer to the parent field so Bun can modify it
-	parentValue := parentField.Interface()
+	// CRITICAL: We need to pass a pointer, not a value, so that when Bun
+	// loads the child records and appends them to the slice, the changes
+	// are reflected in the original struct field.
+	var parentPtr interface{}
+	if parentField.Kind() == reflect.Ptr {
+		// Field is already a pointer (e.g., Parent *Parent), use as-is
+		parentPtr = parentField.Interface()
+	} else {
+		// Field is a value (e.g., Comments []Comment), get its address
+		if parentField.CanAddr() {
+			parentPtr = parentField.Addr().Interface()
+		} else {
+			return fmt.Errorf("cannot get address of field '%s'", parentRelation)
+		}
+	}
 
 	// Load the child relation on the parent record
 	// This uses a shorter alias since we're only loading "Child", not "Parent.Child"
+	// CRITICAL: Use WherePK() to ensure we only load children for THIS specific parent
+	// record, not the first parent in the database table.
 	return b.db.NewSelect().
-		Model(parentValue).
+		Model(parentPtr).
+		WherePK().
 		Relation(childRelation, func(sq *bun.SelectQuery) *bun.SelectQuery {
 			// Apply any custom query modifications
 			if len(apply) > 0 {

pkg/common/recursive_crud.go

@@ -98,6 +98,10 @@ func (p *NestedCUDProcessor) ProcessNestedCUD(
 		}
 	}
 
+	// Filter regularData to only include fields that exist in the model
+	// Use MapToStruct to validate and filter fields
+	regularData = p.filterValidFields(regularData, model)
+
 	// Inject parent IDs for foreign key resolution
 	p.injectForeignKeys(regularData, modelType, parentIDs)
 
@@ -187,6 +191,115 @@ func (p *NestedCUDProcessor) extractCRUDRequest(data map[string]interface{}) str
 	return ""
 }
 
+// filterValidFields filters input data to only include fields that exist in the model
+// Uses reflection.MapToStruct to validate fields and extract only those that match the model
+func (p *NestedCUDProcessor) filterValidFields(data map[string]interface{}, model interface{}) map[string]interface{} {
+	if len(data) == 0 {
+		return data
+	}
+
+	// Create a new instance of the model to use with MapToStruct
+	modelType := reflect.TypeOf(model)
+	for modelType != nil && (modelType.Kind() == reflect.Ptr || modelType.Kind() == reflect.Slice || modelType.Kind() == reflect.Array) {
+		modelType = modelType.Elem()
+	}
+
+	if modelType == nil || modelType.Kind() != reflect.Struct {
+		return data
+	}
+
+	// Create a new instance of the model
+	tempModel := reflect.New(modelType).Interface()
+
+	// Use MapToStruct to map the data - this will only map valid fields
+	err := reflection.MapToStruct(data, tempModel)
+	if err != nil {
+		logger.Debug("Error mapping data to model: %v", err)
+		return data
+	}
+
+	// Extract the mapped fields back into a map
+	// This effectively filters out any fields that don't exist in the model
+	filteredData := make(map[string]interface{})
+	tempModelValue := reflect.ValueOf(tempModel).Elem()
+
+	for key, value := range data {
+		// Check if the field was successfully mapped
+		if fieldWasMapped(tempModelValue, modelType, key) {
+			filteredData[key] = value
+		} else {
+			logger.Debug("Skipping invalid field '%s' - not found in model %v", key, modelType)
+		}
+	}
+
+	return filteredData
+}
+
+// fieldWasMapped checks if a field with the given key was mapped to the model
+func fieldWasMapped(modelValue reflect.Value, modelType reflect.Type, key string) bool {
+	// Look for the field by JSON tag or field name
+	for i := 0; i < modelType.NumField(); i++ {
+		field := modelType.Field(i)
+
+		// Skip unexported fields
+		if !field.IsExported() {
+			continue
+		}
+
+		// Check JSON tag
+		jsonTag := field.Tag.Get("json")
+		if jsonTag != "" && jsonTag != "-" {
+			parts := strings.Split(jsonTag, ",")
+			if len(parts) > 0 && parts[0] == key {
+				return true
+			}
+		}
+
+		// Check bun tag
+		bunTag := field.Tag.Get("bun")
+		if bunTag != "" && bunTag != "-" {
+			if colName := reflection.ExtractColumnFromBunTag(bunTag); colName == key {
+				return true
+			}
+		}
+
+		// Check gorm tag
+		gormTag := field.Tag.Get("gorm")
+		if gormTag != "" && gormTag != "-" {
+			if colName := reflection.ExtractColumnFromGormTag(gormTag); colName == key {
+				return true
+			}
+		}
+
+		// Check lowercase field name
+		if strings.EqualFold(field.Name, key) {
+			return true
+		}
+
+		// Handle embedded structs recursively
+		if field.Anonymous {
+			fieldType := field.Type
+			if fieldType.Kind() == reflect.Ptr {
+				fieldType = fieldType.Elem()
+			}
+			if fieldType.Kind() == reflect.Struct {
+				embeddedValue := modelValue.Field(i)
+				if embeddedValue.Kind() == reflect.Ptr {
+					if embeddedValue.IsNil() {
+						continue
+					}
+					embeddedValue = embeddedValue.Elem()
+				}
+				if fieldWasMapped(embeddedValue, fieldType, key) {
+					return true
+				}
+			}
+		}
+	}
+
+	return false
+}
+
 // injectForeignKeys injects parent IDs into data for foreign key fields
 func (p *NestedCUDProcessor) injectForeignKeys(data map[string]interface{}, modelType reflect.Type, parentIDs map[string]interface{}) {
 	if len(parentIDs) == 0 {

pkg/dbmanager/config.go

@@ -128,7 +128,7 @@ func DefaultManagerConfig() ManagerConfig {
 		RetryAttempts:       3,
 		RetryDelay:          1 * time.Second,
 		RetryMaxDelay:       10 * time.Second,
-		HealthCheckInterval: 30 * time.Second,
+		HealthCheckInterval: 15 * time.Second,
 		EnableAutoReconnect: true,
 	}
 }
@@ -161,6 +161,11 @@ func (c *ManagerConfig) ApplyDefaults() {
 	if c.HealthCheckInterval == 0 {
 		c.HealthCheckInterval = defaults.HealthCheckInterval
 	}
+	// EnableAutoReconnect defaults to true - apply if not explicitly set
+	// Since this is a boolean, we apply the default unconditionally when it's false
+	if !c.EnableAutoReconnect {
+		c.EnableAutoReconnect = defaults.EnableAutoReconnect
+	}
 }
 
 // Validate validates the manager configuration

pkg/dbmanager/manager.go

@@ -219,9 +219,10 @@ func (m *connectionManager) Connect(ctx context.Context) error {
 		logger.Info("Database connection established: name=%s, type=%s", name, connCfg.Type)
 	}
 
-	// Start background health checks if enabled
+	// Always start background health checks
-	if m.config.EnableAutoReconnect && m.config.HealthCheckInterval > 0 {
+	if m.config.HealthCheckInterval > 0 {
 		m.startHealthChecker()
+		logger.Info("Background health checker started: interval=%v", m.config.HealthCheckInterval)
 	}
 
 	logger.Info("Database manager initialized: connections=%d", len(m.connections))

pkg/dbmanager/manager_test.go

@@ -0,0 +1,226 @@
+package dbmanager
+
+import (
+	"context"
+	"database/sql"
+	"testing"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func TestBackgroundHealthChecker(t *testing.T) {
+	// Create a SQLite in-memory database
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	// Create manager config with a short health check interval for testing
+	cfg := ManagerConfig{
+		DefaultConnection: "test",
+		Connections: map[string]ConnectionConfig{
+			"test": {
+				Name:     "test",
+				Type:     DatabaseTypeSQLite,
+				FilePath: ":memory:",
+			},
+		},
+		HealthCheckInterval: 1 * time.Second, // Short interval for testing
+		EnableAutoReconnect: true,
+	}
+
+	// Create manager
+	mgr, err := NewManager(cfg)
+	if err != nil {
+		t.Fatalf("Failed to create manager: %v", err)
+	}
+
+	// Connect - this should start the background health checker
+	ctx := context.Background()
+	err = mgr.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer mgr.Close()
+
+	// Get the connection to verify it's healthy
+	conn, err := mgr.Get("test")
+	if err != nil {
+		t.Fatalf("Failed to get connection: %v", err)
+	}
+
+	// Verify initial health check
+	err = conn.HealthCheck(ctx)
+	if err != nil {
+		t.Errorf("Initial health check failed: %v", err)
+	}
+
+	// Wait for a few health check cycles
+	time.Sleep(3 * time.Second)
+
+	// Get stats to verify the connection is still healthy
+	stats := conn.Stats()
+	if stats == nil {
+		t.Fatal("Expected stats to be returned")
+	}
+
+	if !stats.Connected {
+		t.Error("Expected connection to still be connected")
+	}
+
+	if stats.HealthCheckStatus == "" {
+		t.Error("Expected health check status to be set")
+	}
+
+	// Verify the manager has started the health checker
+	if cm, ok := mgr.(*connectionManager); ok {
+		if cm.healthTicker == nil {
+			t.Error("Expected health ticker to be running")
+		}
+	}
+}
+
+func TestDefaultHealthCheckInterval(t *testing.T) {
+	// Verify the default health check interval is 15 seconds
+	defaults := DefaultManagerConfig()
+
+	expectedInterval := 15 * time.Second
+	if defaults.HealthCheckInterval != expectedInterval {
+		t.Errorf("Expected default health check interval to be %v, got %v",
+			expectedInterval, defaults.HealthCheckInterval)
+	}
+
+	if !defaults.EnableAutoReconnect {
+		t.Error("Expected EnableAutoReconnect to be true by default")
+	}
+}
+
+func TestApplyDefaultsEnablesAutoReconnect(t *testing.T) {
+	// Create a config without setting EnableAutoReconnect
+	cfg := ManagerConfig{
+		Connections: map[string]ConnectionConfig{
+			"test": {
+				Name:     "test",
+				Type:     DatabaseTypeSQLite,
+				FilePath: ":memory:",
+			},
+		},
+	}
+
+	// Verify it's false initially (Go's zero value for bool)
+	if cfg.EnableAutoReconnect {
+		t.Error("Expected EnableAutoReconnect to be false before ApplyDefaults")
+	}
+
+	// Apply defaults
+	cfg.ApplyDefaults()
+
+	// Verify it's now true
+	if !cfg.EnableAutoReconnect {
+		t.Error("Expected EnableAutoReconnect to be true after ApplyDefaults")
+	}
+
+	// Verify health check interval is also set
+	if cfg.HealthCheckInterval != 15*time.Second {
+		t.Errorf("Expected health check interval to be 15s, got %v", cfg.HealthCheckInterval)
+	}
+}
+
+func TestManagerHealthCheck(t *testing.T) {
+	// Create a SQLite in-memory database
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("Failed to open database: %v", err)
+	}
+	defer db.Close()
+
+	// Create manager config
+	cfg := ManagerConfig{
+		DefaultConnection: "test",
+		Connections: map[string]ConnectionConfig{
+			"test": {
+				Name:     "test",
+				Type:     DatabaseTypeSQLite,
+				FilePath: ":memory:",
+			},
+		},
+		HealthCheckInterval: 15 * time.Second,
+		EnableAutoReconnect: true,
+	}
+
+	// Create and connect manager
+	mgr, err := NewManager(cfg)
+	if err != nil {
+		t.Fatalf("Failed to create manager: %v", err)
+	}
+
+	ctx := context.Background()
+	err = mgr.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+	defer mgr.Close()
+
+	// Perform health check on all connections
+	err = mgr.HealthCheck(ctx)
+	if err != nil {
+		t.Errorf("Health check failed: %v", err)
+	}
+
+	// Get stats
+	stats := mgr.Stats()
+	if stats == nil {
+		t.Fatal("Expected stats to be returned")
+	}
+
+	if stats.TotalConnections != 1 {
+		t.Errorf("Expected 1 total connection, got %d", stats.TotalConnections)
+	}
+
+	if stats.HealthyCount != 1 {
+		t.Errorf("Expected 1 healthy connection, got %d", stats.HealthyCount)
+	}
+
+	if stats.UnhealthyCount != 0 {
+		t.Errorf("Expected 0 unhealthy connections, got %d", stats.UnhealthyCount)
+	}
+}
+
+func TestManagerStatsAfterClose(t *testing.T) {
+	cfg := ManagerConfig{
+		DefaultConnection: "test",
+		Connections: map[string]ConnectionConfig{
+			"test": {
+				Name:     "test",
+				Type:     DatabaseTypeSQLite,
+				FilePath: ":memory:",
+			},
+		},
+		HealthCheckInterval: 15 * time.Second,
+	}
+
+	mgr, err := NewManager(cfg)
+	if err != nil {
+		t.Fatalf("Failed to create manager: %v", err)
+	}
+
+	ctx := context.Background()
+	err = mgr.Connect(ctx)
+	if err != nil {
+		t.Fatalf("Failed to connect: %v", err)
+	}
+
+	// Close the manager
+	err = mgr.Close()
+	if err != nil {
+		t.Errorf("Failed to close manager: %v", err)
+	}
+
+	// Stats should show no connections
+	stats := mgr.Stats()
+	if stats.TotalConnections != 0 {
+		t.Errorf("Expected 0 total connections after close, got %d", stats.TotalConnections)
+	}
+}

pkg/reflection/model_utils.go

@@ -1370,6 +1370,63 @@ func convertToFloat64(value interface{}) (float64, bool) {
 	return 0, false
 }
 
+// GetValidJSONFieldNames returns a map of valid JSON field names for a model
+// This can be used to validate input data against a model's structure
+// The map keys are the JSON field names (from json tags) that exist in the model
+func GetValidJSONFieldNames(modelType reflect.Type) map[string]bool {
+	validFields := make(map[string]bool)
+
+	// Unwrap pointers to get to the base struct type
+	for modelType != nil && modelType.Kind() == reflect.Pointer {
+		modelType = modelType.Elem()
+	}
+
+	if modelType == nil || modelType.Kind() != reflect.Struct {
+		return validFields
+	}
+
+	collectValidFieldNames(modelType, validFields)
+	return validFields
+}
+
+// collectValidFieldNames recursively collects valid JSON field names from a struct type
+func collectValidFieldNames(typ reflect.Type, validFields map[string]bool) {
+	for i := 0; i < typ.NumField(); i++ {
+		field := typ.Field(i)
+
+		// Skip unexported fields
+		if !field.IsExported() {
+			continue
+		}
+
+		// Check for embedded structs
+		if field.Anonymous {
+			fieldType := field.Type
+			if fieldType.Kind() == reflect.Ptr {
+				fieldType = fieldType.Elem()
+			}
+			if fieldType.Kind() == reflect.Struct {
+				// Recursively add fields from embedded struct
+				collectValidFieldNames(fieldType, validFields)
+				continue
+			}
+		}
+
+		// Get the JSON tag name for this field (same logic as MapToStruct)
+		jsonTag := field.Tag.Get("json")
+		if jsonTag != "" && jsonTag != "-" {
+			// Extract the field name from the JSON tag (before any options like omitempty)
+			parts := strings.Split(jsonTag, ",")
+			if len(parts) > 0 && parts[0] != "" {
+				validFields[parts[0]] = true
+			}
+		} else {
+			// If no JSON tag, use the field name in lowercase as a fallback
+			validFields[strings.ToLower(field.Name)] = true
+		}
+	}
+}
+
 // getRelationModelSingleLevel gets the model type for a single level field (non-recursive)
 // This is a helper function used by GetRelationModel to handle one level at a time
 func getRelationModelSingleLevel(model interface{}, fieldName string) interface{} {

pkg/restheadspec/HEADERS.md

@@ -214,14 +214,25 @@ x-expand: department:id,name,code
 **Note:** Currently, expand falls back to preload behavior. Full JOIN expansion is planned for future implementation.
 
 #### `x-custom-sql-join`
-Raw SQL JOIN statement.
+Custom SQL JOIN clauses for joining tables in queries.
 
-**Format:** SQL JOIN clause
+**Format:** SQL JOIN clause or multiple clauses separated by `|`
+
+**Single JOIN:**
 ```
 x-custom-sql-join: LEFT JOIN departments d ON d.id = employees.department_id
 ```
 
-⚠️ **Note:** Not yet fully implemented.
+**Multiple JOINs:**
+```
+x-custom-sql-join: LEFT JOIN departments d ON d.id = e.dept_id | INNER JOIN roles r ON r.id = e.role_id
+```
+
+**Features:**
+- Supports any type of JOIN (INNER, LEFT, RIGHT, FULL, CROSS)
+- Multiple JOINs can be specified using the pipe `|` separator
+- JOINs are sanitized for security
+- Can be specified via headers or query parameters
 
 ---
 

pkg/restheadspec/cache_helpers.go

@@ -26,6 +26,7 @@ type queryCacheKey struct {
 	Sort           []common.SortOption   `json:"sort"`
 	CustomSQLWhere string                `json:"custom_sql_where,omitempty"`
 	CustomSQLOr    string                `json:"custom_sql_or,omitempty"`
+	CustomSQLJoin  []string              `json:"custom_sql_join,omitempty"`
 	Expand         []expandOptionKey     `json:"expand,omitempty"`
 	Distinct       bool                  `json:"distinct,omitempty"`
 	CursorForward  string                `json:"cursor_forward,omitempty"`
@@ -40,7 +41,7 @@ type cachedTotal struct {
 // buildExtendedQueryCacheKey builds a cache key for extended query options (restheadspec)
 // Includes expand, distinct, and cursor pagination options
 func buildExtendedQueryCacheKey(tableName string, filters []common.FilterOption, sort []common.SortOption,
-	customWhere, customOr string, expandOpts []interface{}, distinct bool, cursorFwd, cursorBwd string) string {
+	customWhere, customOr string, customJoin []string, expandOpts []interface{}, distinct bool, cursorFwd, cursorBwd string) string {
 
 	key := queryCacheKey{
 		TableName:      tableName,
@@ -48,6 +49,7 @@ func buildExtendedQueryCacheKey(tableName string, filters []common.FilterOption,
 		Sort:           sort,
 		CustomSQLWhere: customWhere,
 		CustomSQLOr:    customOr,
+		CustomSQLJoin:  customJoin,
 		Distinct:       distinct,
 		CursorForward:  cursorFwd,
 		CursorBackward: cursorBwd,
@@ -75,8 +77,8 @@ func buildExtendedQueryCacheKey(tableName string, filters []common.FilterOption,
 	jsonData, err := json.Marshal(key)
 	if err != nil {
 		// Fallback to simple string concatenation if JSON fails
-		return hashString(fmt.Sprintf("%s_%v_%v_%s_%s_%v_%v_%s_%s",
+		return hashString(fmt.Sprintf("%s_%v_%v_%s_%s_%v_%v_%v_%s_%s",
-			tableName, filters, sort, customWhere, customOr, expandOpts, distinct, cursorFwd, cursorBwd))
+			tableName, filters, sort, customWhere, customOr, customJoin, expandOpts, distinct, cursorFwd, cursorBwd))
 	}
 
 	return hashString(string(jsonData))

pkg/restheadspec/handler.go

@@ -502,6 +502,15 @@ func (h *Handler) handleRead(ctx context.Context, w common.ResponseWriter, id st
 		}
 	}
 
+	// Apply custom SQL JOIN clauses
+	if len(options.CustomSQLJoin) > 0 {
+		for _, joinClause := range options.CustomSQLJoin {
+			logger.Debug("Applying custom SQL JOIN: %s", joinClause)
+			// Joins are already sanitized during parsing, so we can apply them directly
+			query = query.Join(joinClause)
+		}
+	}
+
 	// If ID is provided, filter by ID
 	if id != "" {
 		pkName := reflection.GetPrimaryKeyName(model)
@@ -552,6 +561,7 @@ func (h *Handler) handleRead(ctx context.Context, w common.ResponseWriter, id st
 				options.Sort,
 				options.CustomSQLWhere,
 				options.CustomSQLOr,
+				options.CustomSQLJoin,
 				expandOpts,
 				options.Distinct,
 				options.CursorForward,
@@ -883,7 +893,7 @@ func (h *Handler) applyPreloadWithRecursion(query common.SelectQuery, preload co
 	})
 
 	// Handle recursive preloading
-	if preload.Recursive && depth < 5 {
+	if preload.Recursive && depth < 4 {
 		logger.Debug("Applying recursive preload for %s at depth %d", preload.Relation, depth+1)
 
 		// For recursive relationships, we need to get the last part of the relation path

pkg/restheadspec/headers.go

@@ -26,7 +26,8 @@ type ExtendedRequestOptions struct {
 	CustomSQLOr    string
 
 	// Joins
-	Expand []ExpandOption
+	Expand        []ExpandOption
+	CustomSQLJoin []string // Custom SQL JOIN clauses
 
 	// Advanced features
 	AdvancedSQL map[string]string // Column -> SQL expression
@@ -111,6 +112,7 @@ func (h *Handler) parseOptionsFromHeaders(r common.Request, model interface{}) E
 		AdvancedSQL:          make(map[string]string),
 		ComputedQL:           make(map[string]string),
 		Expand:               make([]ExpandOption, 0),
+		CustomSQLJoin:        make([]string, 0),
 		ResponseFormat:       "simple", // Default response format
 		SingleRecordAsObject: true,     // Default: normalize single-element arrays to objects
 	}
@@ -185,8 +187,7 @@ func (h *Handler) parseOptionsFromHeaders(r common.Request, model interface{}) E
 		case strings.HasPrefix(key, "x-expand"):
 			h.parseExpand(&options, decodedValue)
 		case strings.HasPrefix(key, "x-custom-sql-join"):
-			// TODO: Implement custom SQL join
+			h.parseCustomSQLJoin(&options, decodedValue)
-			logger.Debug("Custom SQL join not yet implemented: %s", decodedValue)
 
 		// Sorting & Pagination
 		case strings.HasPrefix(key, "x-sort"):
@@ -495,6 +496,43 @@ func (h *Handler) parseExpand(options *ExtendedRequestOptions, value string) {
 	}
 }
 
+// parseCustomSQLJoin parses x-custom-sql-join header
+// Format: Single JOIN clause or multiple JOIN clauses separated by |
+// Example: "LEFT JOIN departments d ON d.id = employees.department_id"
+// Example: "LEFT JOIN departments d ON d.id = e.dept_id | INNER JOIN roles r ON r.id = e.role_id"
+func (h *Handler) parseCustomSQLJoin(options *ExtendedRequestOptions, value string) {
+	if value == "" {
+		return
+	}
+
+	// Split by | for multiple joins
+	joins := strings.Split(value, "|")
+	for _, joinStr := range joins {
+		joinStr = strings.TrimSpace(joinStr)
+		if joinStr == "" {
+			continue
+		}
+
+		// Basic validation: should contain "JOIN" keyword
+		upperJoin := strings.ToUpper(joinStr)
+		if !strings.Contains(upperJoin, "JOIN") {
+			logger.Warn("Invalid custom SQL join (missing JOIN keyword): %s", joinStr)
+			continue
+		}
+
+		// Sanitize the join clause using common.SanitizeWhereClause
+		// Note: This is basic sanitization - in production you may want stricter validation
+		sanitizedJoin := common.SanitizeWhereClause(joinStr, "", nil)
+		if sanitizedJoin == "" {
+			logger.Warn("Custom SQL join failed sanitization: %s", joinStr)
+			continue
+		}
+
+		logger.Debug("Adding custom SQL join: %s", sanitizedJoin)
+		options.CustomSQLJoin = append(options.CustomSQLJoin, sanitizedJoin)
+	}
+}
+
 // parseSorting parses x-sort header
 // Format: +field1,-field2,field3 (+ for ASC, - for DESC, default ASC)
 func (h *Handler) parseSorting(options *ExtendedRequestOptions, value string) {

pkg/restheadspec/query_params_test.go

@@ -301,6 +301,62 @@ func TestParseOptionsFromQueryParams(t *testing.T) {
 				}
 			},
 		},
+		{
+			name: "Parse custom SQL JOIN from query params",
+			queryParams: map[string]string{
+				"x-custom-sql-join": `LEFT JOIN departments d ON d.id = employees.department_id`,
+			},
+			validate: func(t *testing.T, options ExtendedRequestOptions) {
+				if len(options.CustomSQLJoin) == 0 {
+					t.Error("Expected CustomSQLJoin to be set")
+					return
+				}
+				if len(options.CustomSQLJoin) != 1 {
+					t.Errorf("Expected 1 custom SQL join, got %d", len(options.CustomSQLJoin))
+					return
+				}
+				expected := `LEFT JOIN departments d ON d.id = employees.department_id`
+				if options.CustomSQLJoin[0] != expected {
+					t.Errorf("Expected CustomSQLJoin[0]=%q, got %q", expected, options.CustomSQLJoin[0])
+				}
+			},
+		},
+		{
+			name: "Parse multiple custom SQL JOINs from query params",
+			queryParams: map[string]string{
+				"x-custom-sql-join": `LEFT JOIN departments d ON d.id = e.dept_id | INNER JOIN roles r ON r.id = e.role_id`,
+			},
+			validate: func(t *testing.T, options ExtendedRequestOptions) {
+				if len(options.CustomSQLJoin) != 2 {
+					t.Errorf("Expected 2 custom SQL joins, got %d", len(options.CustomSQLJoin))
+					return
+				}
+				expected1 := `LEFT JOIN departments d ON d.id = e.dept_id`
+				expected2 := `INNER JOIN roles r ON r.id = e.role_id`
+				if options.CustomSQLJoin[0] != expected1 {
+					t.Errorf("Expected CustomSQLJoin[0]=%q, got %q", expected1, options.CustomSQLJoin[0])
+				}
+				if options.CustomSQLJoin[1] != expected2 {
+					t.Errorf("Expected CustomSQLJoin[1]=%q, got %q", expected2, options.CustomSQLJoin[1])
+				}
+			},
+		},
+		{
+			name: "Parse custom SQL JOIN from headers",
+			headers: map[string]string{
+				"X-Custom-SQL-Join": `LEFT JOIN users u ON u.id = posts.user_id`,
+			},
+			validate: func(t *testing.T, options ExtendedRequestOptions) {
+				if len(options.CustomSQLJoin) == 0 {
+					t.Error("Expected CustomSQLJoin to be set from header")
+					return
+				}
+				expected := `LEFT JOIN users u ON u.id = posts.user_id`
+				if options.CustomSQLJoin[0] != expected {
+					t.Errorf("Expected CustomSQLJoin[0]=%q, got %q", expected, options.CustomSQLJoin[0])
+				}
+			},
+		},
 	}
 
 	for _, tt := range tests {

pkg/restheadspec/restheadspec.go

@@ -32,6 +32,7 @@
 //   - X-Clean-JSON: Boolean to remove null/empty fields
 //   - X-Custom-SQL-Where: Custom SQL WHERE clause (AND)
 //   - X-Custom-SQL-Or: Custom SQL WHERE clause (OR)
+//   - X-Custom-SQL-Join: Custom SQL JOIN clauses (pipe-separated for multiple)
 //
 // # Usage Example
 //