[WIP] Make anitya use authlib instead of social_auth

[LenkaSeg]

Allow authentication with Fedora, GitHub and Google. This PR aims to get rid of the social_auth library and use authlib instead.

Related issue #1139

[LenkaSeg]

What is working so far: authentication with GitHub and Google. What is needed: Fedora, create a new social table in models, do something with the next, so it does not redirect to main page, tests, documentation.

[softwarefactory-project-zuul[bot]]

Build failed. More information on how to proceed and troubleshoot errors available at https://fedoraproject.org/wiki/Zuul-based-ci

• tox-mypy : SUCCESS in 4m 34s
• tox-lint : FAILURE in 4m 07s
• tox-format : FAILURE in 4m 16s
• tox-python38 : FAILURE in 5m 35s
• tox-python39 : FAILURE in 5m 01s
• anitya-tox-docs : FAILURE in 5m 01s
• tox-bandit : SUCCESS in 4m 21s
• tox-diff-cover : FAILURE in 6m 23s

[lgtm-com[bot]]

This pull request introduces 2 alerts when merging ffbba790584edd82c86e3c3861e1916b72b75a3e into b16ca5e7f0d06de07678dce369ef5c49b2792f66 - view on LGTM.com

new alerts:

• 1 for Unused import
• 1 for Module is imported with 'import' and 'import from'

[romulasry]

This would be nice for https://rpmfusion.org/ next. Good job.

[Zlopez]

Because there is now initiative working on Flask OIDC to remove the deprecated parts, we should probably use it instead of using authlib directly.

[romulasry]

https://github.com/fedora-infra/flask-oidc