Motorhead

Changes:

- Added `Service.create()` and `Service.update()` methods.
- Updated the documentation.
- Updated the FastAPI example.

More documentation updates.

Just a documentation update for PyPI.

Added ODM-like query builder and operator implementations (not complete yet).

Migration of [fastapi-motor-oil](https://github.com/volfpeter/fastapi-motor-oil) from Pydantic v1 to v2, and a few minor improvements and fixes.