Add comprehensive tests to verify that Traefik Host rule labels are
generated with the correct format: Host(`domain.com`) with both
opening and closing parentheses.
These tests cover:
- Basic Host rule format validation
- PathPrefix format validation
- Combined Host and PathPrefix rules
- YAML serialization round-trip preservation
- Edge cases for various domain name formats
- Multiple entrypoints (web/websecure)
- Special characters in paths
Related to: #3161