Fastapi-sso

- add support for [Notion](https://notion.so)
- fix: use `additional_headers` for user endpoint

- only allow valid e-mail addresses in OpenID's `email` field

Contributed by parfeniukink

- obtain github users' email even if private
- solution proposed by Cereal84
- pass authenticated session to `openid_from_response`

- add email to default MicrosoftSSO scopes
- do not fail if Microsoft API does not return `mail` in its response

- starlette is now an indirect dependency
- added support for Python 3.12
- contributed by parfeniukink

- PEP 561 compliance

credits to parfeniukink

- mostly chores
- import paths can now be shorter
- `from fastapi_sso.sso.base import OpenID` is now available as `from fastapi_sso import OpenID`