v0.4.0: Add tenant extensibility with JSONB metadata support

🎯 Major Features:
- ExtensibleTenant model with JSONB metadata field for flexible tenant data
- ExtensibleRepository with full CRUD operations and metadata querying
- Database migration for metadata column with optimized indexes
- Extension helpers for common integrations (Stripe, branding)
- Comprehensive examples and documentation

🔧 Improvements:
- Fixed compilation errors in flexible-limits example
- Added GitHub Actions workflow for CI/CD
- Comprehensive extensibility guide with best practices

�� Benefits:
- Add external IDs (stripe_customer_id) without schema changes
- High performance JSONB queries with proper indexing
- Backward compatible with existing tenant functionality
- Type-safe helpers for common integration patterns

This enables users to extend tenant functionality for external service
integrations while maintaining excellent performance and developer experience.

v0.3.0 - Add comprehensive unit test suite

- Complete unit and integration test coverage for all components
- 80+ test functions across 9 test files
- Mock implementations for all interfaces
- Integration tests with PostgreSQL database
- Enhanced flexible limits system with additional utility methods
- Improved error handling and nil pointer safety
- Test documentation and setup instructions
- Code formatting with gofmt

v0.2.0: Complete Migration System Implementation

This release implements a fully functional migration system for multi-tenant applications:

New Features:
- Complete MigrationManager implementation using PostgreSQL functions
- Hybrid approach combining proven SQL functions with Go wrapper APIs
- Support for single tenant and bulk tenant migrations
- Migration tracking and rollback capabilities
- File-based migration loading
- Configurable migrations directory

Breaking Changes:
- MigrationsDir must now be configured in DatabaseConfig

Technical Details:
- Ported battle-tested migration functions from constructor-mx backend
- Added transaction safety and comprehensive error handling
- Implemented migration history tracking and status checking
- Full ACID compliance for cross-tenant operations

The library is now 100% functional for production multi-tenant applications.

Fix unused import error and compilation issues

- Fix unused import in database/schema.go by adding interface compliance check
- Fix compilation error in examples/flexible-limits/main.go by commenting out unimplemented functionality
- Ensures package can be imported and used by external projects without compilation errors

Fixes the issue where importing go-multitenant would fail with 'imported and not used' error.

have a more flexible limits system