Refactor keyword enums for clarity and consistency

- Rename `ValidKeywords` to `SupportedKeywords` for better semantic alignment.
- Rename `InvalidKeywords` to `UnsupportedKeywords` for improved clarity.
- Update references across the module to reflect these renamed enums.
- Simplify `normalize_string` by removing unnecessary replacement.
- Adjust property methods and related logic to accommodate the new naming conventions.