Support explicit redirect host source selection for HTTP-to-HTTPS redirects with ordered header lookup, fixed host mode, and strict validation. Document the new redirect option relationships and add focused tests for 426 fallback, conflict checks, and non-graceful startup errors.
- Implement ShouldBind with support for JSON, Form, WANF, and GOB formats
- Add ShouldBindForm, ShouldBindGOB, and helper functions for form binding
- Use fmt.Appendf instead of fmt.Sprintf for better performance
- Replace interface{} with any for modern Go style
- Use maps.Copy for cleaner header copying
- Update strings.SplitSeq to use range over strings.Seq
- Remove deprecated placeholder comments and add proper implementations
- Fix reflect.Pointer usage for Go 1.22+ compatibility
