[FEATURE] Offload user managment

[arunoruto]

Is your feature request related to a problem? Please describe.
Sometimes, it's a bit cumbersome to keep all the self-hosted service accounts up-to-date, so it would be nice to offload this to a different platform. Creating a sign-in with GitHub and/or Google would be amazing.

Describe the solution you'd like
We can create a user account using an identity provider of our choice (given from a list of supported providers). Something similar has been implemented in calibre-web and many other services.

Describe alternatives you've considered
Maybe we can disable accounts and manage access through a proxy layer like Authelia or Cloudflare applications. But then managing user data would become more complicated!

Additional context
Since the accounts would be needed to log in for OPDS, one would need an alternative password, like a token.
This would be similar to #246 with a more specific scenario.