feat(security): add query mode handling for database operations

* Introduced QueryMode to select between stored procedure and direct SQL execution.
* Implemented dbCapability to probe for stored procedure existence.
* Added table names configuration for direct SQL operations.
* Updated DatabaseTwoFactorProvider to support query mode and table names.
* Implemented direct SQL methods mirroring stored procedures for TOTP operations.
* Added tests for query mode logic and table names validation.

pkg/security/table_names.go

@@ -0,0 +1,101 @@
+package security
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+)
+
+// ErrDirectModeUnsupported is returned by Direct-mode operations that have no
+// portable equivalent because they depend on an external schema this package
+// does not own (e.g. core.secaccess / core.hub_link for column/row security).
+// Callers needing that functionality must run against Postgres with the
+// resolvespec_column_security / resolvespec_row_security stored procedures
+// installed (ModeProcedure or ModeAuto with the procedures present).
+var ErrDirectModeUnsupported = errors.New("direct mode does not support column/row security; requires the resolvespec_column_security/resolvespec_row_security stored procedures")
+
+// TableNames defines all configurable table names used by Direct-mode SQL
+// in the security package. Override individual fields to remap to custom
+// table names. Use DefaultTableNames() for baseline defaults, and
+// MergeTableNames() to apply partial overrides.
+type TableNames struct {
+	Users                  string // default: "users"
+	UserSessions           string // default: "user_sessions"
+	TokenBlacklist         string // default: "token_blacklist"
+	UserTOTPBackupCodes    string // default: "user_totp_backup_codes"
+	UserPasskeyCredentials string // default: "user_passkey_credentials"
+	UserPasswordResets     string // default: "user_password_resets"
+	OAuthClients           string // default: "oauth_clients"
+	OAuthCodes             string // default: "oauth_codes"
+}
+
+// DefaultTableNames returns a TableNames with all default table names.
+func DefaultTableNames() *TableNames {
+	return &TableNames{
+		Users:                  "users",
+		UserSessions:           "user_sessions",
+		TokenBlacklist:         "token_blacklist",
+		UserTOTPBackupCodes:    "user_totp_backup_codes",
+		UserPasskeyCredentials: "user_passkey_credentials",
+		UserPasswordResets:     "user_password_resets",
+		OAuthClients:           "oauth_clients",
+		OAuthCodes:             "oauth_codes",
+	}
+}
+
+// MergeTableNames returns a copy of base with any non-empty fields from override applied.
+// If override is nil, a copy of base is returned.
+func MergeTableNames(base, override *TableNames) *TableNames {
+	if override == nil {
+		copied := *base
+		return &copied
+	}
+	merged := *base
+	if override.Users != "" {
+		merged.Users = override.Users
+	}
+	if override.UserSessions != "" {
+		merged.UserSessions = override.UserSessions
+	}
+	if override.TokenBlacklist != "" {
+		merged.TokenBlacklist = override.TokenBlacklist
+	}
+	if override.UserTOTPBackupCodes != "" {
+		merged.UserTOTPBackupCodes = override.UserTOTPBackupCodes
+	}
+	if override.UserPasskeyCredentials != "" {
+		merged.UserPasskeyCredentials = override.UserPasskeyCredentials
+	}
+	if override.UserPasswordResets != "" {
+		merged.UserPasswordResets = override.UserPasswordResets
+	}
+	if override.OAuthClients != "" {
+		merged.OAuthClients = override.OAuthClients
+	}
+	if override.OAuthCodes != "" {
+		merged.OAuthCodes = override.OAuthCodes
+	}
+	return &merged
+}
+
+// ValidateTableNames checks that all non-empty fields in names are valid SQL identifiers.
+func ValidateTableNames(names *TableNames) error {
+	v := reflect.ValueOf(names).Elem()
+	typ := v.Type()
+	for i := 0; i < v.NumField(); i++ {
+		field := v.Field(i)
+		if field.Kind() != reflect.String {
+			continue
+		}
+		val := field.String()
+		if val != "" && !validSQLIdentifier.MatchString(val) {
+			return fmt.Errorf("TableNames.%s contains invalid characters: %q", typ.Field(i).Name, val)
+		}
+	}
+	return nil
+}
+
+// resolveTableNames merges an optional override with defaults.
+func resolveTableNames(override *TableNames) *TableNames {
+	return MergeTableNames(DefaultTableNames(), override)
+}