Updated Readme files

pkg/writers/pgsql/README.md

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+# PostgreSQL Writer
+
+Generates PostgreSQL DDL (Data Definition Language) SQL scripts from database schema information.
+
+## Overview
+
+The PostgreSQL Writer converts RelSpec's internal database model representation into PostgreSQL-compatible SQL DDL scripts, including CREATE TABLE statements, constraints, indexes, views, and sequences.
+
+## Features
+
+- Generates complete PostgreSQL DDL
+- Creates schemas, tables, columns
+- Defines constraints (PK, FK, unique, check)
+- Creates indexes
+- Generates views and sequences
+- Supports migration scripts
+- Includes audit triggers (optional)
+- Handles PostgreSQL-specific data 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/pgsql"
+)
+
+func main() {
+    options := &writers.WriterOptions{
+        OutputPath: "schema.sql",
+    }
+
+    writer := pgsql.NewWriter(options)
+    err := writer.WriteDatabase(db)
+    if err != nil {
+        panic(err)
+    }
+}
+```
+
+### CLI Examples
+
+```bash
+# Generate PostgreSQL DDL from JSON schema
+relspec --input json \
+  --in-file schema.json \
+  --output pgsql \
+  --out-file schema.sql
+
+# Convert GORM models to PostgreSQL DDL
+relspec --input gorm \
+  --in-file models.go \
+  --output pgsql \
+  --out-file create_tables.sql
+
+# Export live database schema to SQL
+relspec --input pgsql \
+  --conn "postgres://localhost/source_db" \
+  --output pgsql \
+  --out-file backup_schema.sql
+```
+
+## Generated SQL Example
+
+```sql
+-- Schema: public
+
+CREATE SCHEMA IF NOT EXISTS public;
+
+-- Table: public.users
+
+CREATE TABLE IF NOT EXISTS public.users (
+    id BIGSERIAL PRIMARY KEY,
+    username VARCHAR(50) NOT NULL,
+    email VARCHAR(100) NOT NULL,
+    bio TEXT,
+    created_at TIMESTAMP NOT NULL DEFAULT NOW()
+);
+
+-- Constraints for public.users
+
+ALTER TABLE public.users
+    ADD CONSTRAINT uq_users_username UNIQUE (username);
+
+-- Indexes for public.users
+
+CREATE INDEX idx_users_email ON public.users (email);
+
+-- Table: public.posts
+
+CREATE TABLE IF NOT EXISTS public.posts (
+    id BIGSERIAL PRIMARY KEY,
+    user_id BIGINT NOT NULL,
+    title VARCHAR(200) NOT NULL,
+    content TEXT,
+    created_at TIMESTAMP DEFAULT NOW()
+);
+
+-- Foreign Keys for public.posts
+
+ALTER TABLE public.posts
+    ADD CONSTRAINT fk_posts_user_id
+    FOREIGN KEY (user_id)
+    REFERENCES public.users (id)
+    ON DELETE CASCADE
+    ON UPDATE NO ACTION;
+
+-- Indexes for public.posts
+
+CREATE INDEX idx_posts_user_id ON public.posts (user_id);
+```
+
+## Writer Options
+
+### Metadata Options
+
+```go
+options := &writers.WriterOptions{
+    OutputPath: "schema.sql",
+    Metadata: map[string]interface{}{
+        "include_drop":    true,  // Include DROP statements
+        "include_audit":   true,  // Include audit triggers
+        "if_not_exists":   true,  // Use IF NOT EXISTS
+        "migration_mode":  false, // Generate migration script
+    },
+}
+```
+
+## Features
+
+### Full DDL Generation
+
+Generates complete database structure:
+- CREATE SCHEMA statements
+- CREATE TABLE with all columns and types
+- PRIMARY KEY constraints
+- FOREIGN KEY constraints with actions
+- UNIQUE constraints
+- CHECK constraints
+- CREATE INDEX statements
+- CREATE VIEW statements
+- CREATE SEQUENCE statements
+
+### Migration Mode
+
+When `migration_mode` is enabled, generates migration scripts with:
+- Version tracking
+- Up/down migrations
+- Transactional DDL
+- Rollback support
+
+### Audit Triggers
+
+When `include_audit` is enabled, adds:
+- Created/updated timestamp triggers
+- Audit logging functionality
+- Change tracking
+
+## PostgreSQL-Specific Features
+
+- Serial types (SERIAL, BIGSERIAL)
+- Advanced types (UUID, JSONB, ARRAY)
+- Schema-qualified names
+- Constraint actions (CASCADE, RESTRICT, SET NULL)
+- Partial indexes
+- Function-based indexes
+- Check constraints with expressions
+
+## Data Types
+
+Supports all PostgreSQL data types:
+- Integer types: SMALLINT, INTEGER, BIGINT, SERIAL, BIGSERIAL
+- Numeric types: NUMERIC, DECIMAL, REAL, DOUBLE PRECISION
+- String types: VARCHAR, CHAR, TEXT
+- Date/Time: DATE, TIME, TIMESTAMP, TIMESTAMPTZ, INTERVAL
+- Boolean: BOOLEAN
+- Binary: BYTEA
+- JSON: JSON, JSONB
+- UUID: UUID
+- Network: INET, CIDR, MACADDR
+- Special: ARRAY, HSTORE
+
+## Notes
+
+- Generated SQL is formatted and readable
+- Comments are preserved from source schema
+- Schema names are fully qualified
+- Default values are properly quoted
+- Constraint names follow PostgreSQL conventions
+- Compatible with PostgreSQL 12+