Updated Readme files

pkg/writers/gorm/README.md

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+# GORM Writer
+
+Generates Go source files with GORM model definitions from database schema information.
+
+## Overview
+
+The GORM Writer converts RelSpec's internal database model representation into Go source code with GORM struct definitions, complete with proper tags, relationships, and methods.
+
+## Features
+
+- Generates GORM-compatible Go structs
+- Creates proper `gorm` struct tags
+- Generates `TableName()` methods
+- Adds relationship fields (belongs-to, has-many)
+- Supports both single-file and multi-file output
+- Auto-generates helper methods (optional)
+- Maps SQL types to Go types
+- Handles nullable fields with custom sql_types
+
+## Usage
+
+### Basic Example
+
+```go
+package main
+
+import (
+    "git.warky.dev/wdevs/relspecgo/pkg/models"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers/gorm"
+)
+
+func main() {
+    // Assume db is a *models.Database from a reader
+    options := &writers.WriterOptions{
+        OutputPath:  "models.go",
+        PackageName: "models",
+    }
+
+    writer := gorm.NewWriter(options)
+    err := writer.WriteDatabase(db)
+    if err != nil {
+        panic(err)
+    }
+}
+```
+
+### CLI Examples
+
+```bash
+# Generate GORM models from PostgreSQL database (single file)
+relspec --input pgsql \
+  --conn "postgres://localhost/mydb" \
+  --output gorm \
+  --out-file models.go \
+  --package models
+
+# Generate GORM models with multi-file output (one file per table)
+relspec --input json \
+  --in-file schema.json \
+  --output gorm \
+  --out-file models/ \
+  --package models
+
+# Convert DBML to GORM models
+relspec --input dbml --in-file schema.dbml --output gorm --out-file models.go
+```
+
+## Output Modes
+
+### Single File Mode
+
+Generates all models in one file:
+
+```bash
+relspec --input pgsql --conn "..." --output gorm --out-file models.go
+```
+
+### Multi-File Mode
+
+Generates one file per table (auto-detected when output is a directory):
+
+```bash
+relspec --input pgsql --conn "..." --output gorm --out-file models/
+```
+
+Files are named: `sql_{schema}_{table}.go`
+
+## Generated Code Example
+
+```go
+package models
+
+import (
+    "time"
+    sql_types "git.warky.dev/wdevs/sql_types"
+)
+
+type ModelUser struct {
+    ID        int64                `gorm:"column:id;type:bigint;primaryKey;autoIncrement" json:"id"`
+    Username  string               `gorm:"column:username;type:varchar(50);not null;uniqueIndex" json:"username"`
+    Email     string               `gorm:"column:email;type:varchar(100);not null" json:"email"`
+    CreatedAt time.Time            `gorm:"column:created_at;type:timestamp;not null;default:now()" json:"created_at"`
+
+    // Relationships
+    Pos []*ModelPost `gorm:"foreignKey:UserID;references:ID;constraint:OnDelete:CASCADE" json:"pos,omitempty"`
+}
+
+func (ModelUser) TableName() string {
+    return "public.users"
+}
+
+type ModelPost struct {
+    ID        int64           `gorm:"column:id;type:bigint;primaryKey" json:"id"`
+    UserID    int64           `gorm:"column:user_id;type:bigint;not null" json:"user_id"`
+    Title     string          `gorm:"column:title;type:varchar(200);not null" json:"title"`
+    Content   sql_types.SqlString `gorm:"column:content;type:text" json:"content,omitempty"`
+
+    // Belongs to
+    Use *ModelUser `gorm:"foreignKey:UserID;references:ID" json:"use,omitempty"`
+}
+
+func (ModelPost) TableName() string {
+    return "public.posts"
+}
+```
+
+## Writer Options
+
+### Metadata Options
+
+Configure the writer behavior using metadata in `WriterOptions`:
+
+```go
+options := &writers.WriterOptions{
+    OutputPath:  "models.go",
+    PackageName: "models",
+    Metadata: map[string]interface{}{
+        "multi_file":      true,  // Enable multi-file mode
+        "populate_refs":   true,  // Populate RefDatabase/RefSchema
+        "generate_get_id_str": true, // Generate GetIDStr() methods
+    },
+}
+```
+
+## Type Mapping
+
+| SQL Type | Go Type | Notes |
+|----------|---------|-------|
+| bigint, int8 | int64 | - |
+| integer, int, int4 | int | - |
+| smallint, int2 | int16 | - |
+| varchar, text | string | Not nullable |
+| varchar, text (nullable) | sql_types.SqlString | Nullable |
+| boolean, bool | bool | - |
+| timestamp, timestamptz | time.Time | - |
+| numeric, decimal | float64 | - |
+| uuid | string | - |
+| json, jsonb | string | - |
+
+## Relationship Generation
+
+The writer automatically generates relationship fields:
+
+- **Belongs-to**: Generated for tables with foreign keys
+- **Has-many**: Generated for tables referenced by foreign keys
+- Relationship field names use 3-letter prefixes
+- Includes proper `gorm` tags with `foreignKey` and `references`
+
+## Notes
+
+- Model names are prefixed with "Model" (e.g., `ModelUser`)
+- Nullable columns use `sql_types.SqlString`, `sql_types.SqlInt64`, etc.
+- Generated code is auto-formatted with `go fmt`
+- JSON tags are automatically added
+- Supports schema-qualified table names in `TableName()` method