- Add ExtensionProvider attribute class to define extension targets
- Convert function-based extensions to class-based ExtensionProvider pattern
- Support various target types including native_types, complex_types, and class names
- Parse ExtensionProvider attributes during preprocessing phase
- Generate proper extension method calls using provider classes
- Update test cases to use ExtensionProvider syntax instead of function prefixes
- Remove old extension function name patterns and related logic
- Add validation for extension provider method signatures and parameters
- Support both snake_case and camel
