- Introduced origContentLength and bodyModified fields to track original content length and body modification status.
- Updated ContentLength and ContentLengthStr methods to return accurate content length based on body modification state.
- Adjusted Write and FlushRelease methods to ensure proper handling of Content-Length header.
- Modified middleware to use the new ContentLengthStr method.
- Replace template syntax ({{ .Request.Method }}) with $-prefixed variables ($req_method)
- Implement custom variable parser with static ($req_method, $status_code) and dynamic ($header(), $arg(), $form()) variables
- Replace templateOrStr interface with templateString struct and ExpandVars methods
- Add parser improvements for reliable quote handling
- Add new error types: ErrUnterminatedParenthesis, ErrUnexpectedVar, ErrExpectOneOrTwoArgs
- Update all tests and help text to use new variable syntax
- Add comprehensive unit and benchmark tests for variable expansion