Refactor API endpoints and update OpenAPI schema

- Updated OpenAPI schema to reflect changes in API endpoints.
- Renamed parameters in API calls for consistency, changing `column_name` to `columns` in lineage-related endpoints.
- Adjusted the handling of optional properties in the `ModelSQLMeshModel` class to ensure default values are set.
- Changed route parameter types from `str` to `path` for better URL handling in several endpoints.

These changes improve the clarity and functionality of the API.

Author: vishnu