Update to FastAPI 0.80 (f8bd04a)

This release will update/upgrade to FastAPI 0.80.
This is a minor release to align with FastAPI's versioning strategy.
BREAKING CHANGE: `response_model` will now invalidate `None`.
https://github.com/tiangolo/fastapi/releases/tag/0.80.0

Commits:

- Bump version from 0.28.1 to 0.29.0 (eceeb09)
- Update to FastAPI 0.80 (f8bd04a)
- Update dependencies (cd301e6)