feat: unify store initialization with flexible option-based API

- Replace legacy initialization functions with a unified NewStore() using the Option Pattern
- Add extensive configuration options for connection, authentication, Redis, and session settings
- Implement strict validation for configuration and connection options at initialization
- Remove code duplication and improve separation of concerns in store setup
- Update documentation and usage examples for the new API
- Add a comprehensive migration guide for upgrading from v1 to v2
- Update module path to github.com/boj/redistore/v2 for semantic versioning
- Improve error messages and fail-fast behavior for invalid configurations
- Add a new test suite with thorough coverage for option validation and error handling
- Deprecate v1 API and document migration steps
- Enhance developer experience with clearer, more flexible, and self-documenting options

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

Author: appleboy

CHANGELOG.md

@@ -0,0 +1,157 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [2.0.0] - 2026-01-13
+
+### Breaking Changes
+
+This is a major version update with breaking API changes. Please see [MIGRATION.md](MIGRATION.md) for detailed migration instructions.
+
+#### Removed
+
+- **`NewRediStore(size, network, address, username, password, keyPairs)`** - Replaced by `NewStore()` with `WithAddress()` option
+- **`NewRediStoreWithDB(size, network, address, username, password, db, keyPairs)`** - Replaced by `NewStore()` with `WithAddress()` and `WithDB()` options
+- **`NewRediStoreWithPool(pool, keyPairs)`** - Replaced by `NewStore()` with `WithPool()` option
+- **`NewRediStoreWithURL(size, url, keyPairs)`** - Replaced by `NewStore()` with `WithURL()` option
+
+### Added
+
+#### New API
+
+- **`NewStore(keyPairs, opts...)`** - New unified initialization function using Option Pattern
+
+  ```go
+  store, err := NewStore(
+      []byte("secret-key"),
+      WithAddress("tcp", ":6379"),
+      WithDB("1"),
+      WithMaxLength(8192),
+  )
+  ```
+
+#### Connection Options
+
+- **`WithPool(pool)`** - Use custom Redis connection pool
+- **`WithAddress(network, address)`** - Connect using network protocol and address
+- **`WithURL(url)`** - Connect using Redis URL
+
+#### Authentication Options
+
+- **`WithAuth(username, password)`** - Set username and password for Redis authentication
+- **`WithPassword(password)`** - Set password only (convenience function)
+
+#### Redis Configuration Options
+
+- **`WithDB(db)`** - Set Redis database index as string ("0"-"15")
+- **`WithDBNum(dbNum)`** - Set Redis database index as integer (0-15)
+- **`WithPoolSize(size)`** - Set connection pool size (default: 10)
+- **`WithIdleTimeout(timeout)`** - Set connection idle timeout (default: 240s)
+
+#### Store Configuration Options
+
+- **`WithMaxLength(length)`** - Set maximum session data size (default: 4096 bytes)
+- **`WithKeyPrefix(prefix)`** - Set Redis key prefix (default: "session\_")
+- **`WithDefaultMaxAge(age)`** - Set default TTL in seconds (default: 1200)
+- **`WithSerializer(serializer)`** - Set session serializer (default: GobSerializer)
+- **`WithSessionOptions(opts)`** - Set full session options
+- **`WithPath(path)`** - Set cookie path (default: "/")
+- **`WithMaxAge(age)`** - Set cookie MaxAge (default: 30 days)
+
+#### Testing
+
+- **`redistore_options_test.go`** - Comprehensive test suite for option validation
+- Added 23+ new tests covering:
+  - Configuration validation
+  - Error handling
+  - Option combinations
+  - Default values
+
+### Changed
+
+- Module path updated to `github.com/boj/redistore/v2` for v2 versioning
+- Improved error messages with detailed context
+- Configuration validation moved to initialization time (fail fast)
+
+### Improved
+
+- **Code Quality**
+
+  - Eliminated code duplication across initialization functions
+  - Better separation of concerns with internal configuration structures
+  - More maintainable and extensible codebase
+
+- **API Design**
+
+  - Self-documenting option names
+  - Compile-time validation of configuration
+  - Flexible option combinations
+  - Better default values
+
+- **Developer Experience**
+  - Single entry point reduces learning curve
+  - Options can be applied in any order
+  - Clear error messages for invalid configurations
+  - Comprehensive documentation
+
+### Fixed
+
+- Connection validation now happens during initialization (not on first use)
+- Better handling of nil values in configuration
+- Improved database number validation (0-15 range)
+
+### Documentation
+
+- **Added `MIGRATION.md`** - Comprehensive migration guide from v1 to v2
+- **Added `CHANGELOG.md`** - Version history and change tracking
+- Updated all code examples to use new API
+- Improved inline documentation with examples
+
+### Technical Details
+
+#### Internal Changes
+
+- Added `Option` function type for configuration
+- Added `storeConfig` struct for internal configuration management
+- Added `addressConfig` struct for network address configuration
+- Implemented `defaultConfig()` for sensible defaults
+- Implemented `validate()` for configuration validation
+- Implemented `buildPool()` for pool creation from configuration
+
+#### Compatibility
+
+- **Go Version**: Requires Go 1.23+
+- **Dependencies**: No changes to external dependencies
+  - `github.com/gomodule/redigo v1.9.3`
+  - `github.com/gorilla/securecookie v1.1.2`
+  - `github.com/gorilla/sessions v1.4.0`
+
+## [1.0.0] - Previous Releases
+
+For changes prior to v2.0.0, please refer to the git history.
+
+### v1 API (Deprecated)
+
+The v1 API included four initialization functions:
+
+- `NewRediStore()` - Basic initialization
+- `NewRediStoreWithDB()` - With database selection
+- `NewRediStoreWithPool()` - With custom pool
+- `NewRediStoreWithURL()` - With Redis URL
+
+These have been replaced by the unified `NewStore()` function with options in v2.
+
+---
+
+## Migration Guide
+
+See [MIGRATION.md](MIGRATION.md) for step-by-step instructions on upgrading from v1 to v2.
+
+## Support
+
+- **Issues**: https://github.com/boj/redistore/issues
+- **Discussions**: https://github.com/boj/redistore/discussions
+- **Documentation**: https://pkg.go.dev/github.com/boj/redistore/v2