SSO support (OAuth2/OIDC, LDAP)

Is your feature request related to a problem? Please describe. Managing users for a server which provides multiple services (Mastodon, Matrix, bookwyrm) gets tedious without a central user store. This can be solved by using exactly that and simplifying login using SSO.

Describe the solution you'd like It would be nice to be able to Sign in (and create if needed) users using the OpenID Connect standard.

Describe alternatives you've considered Alternatively, backing the user store using LDAP could be an option, but is less preferred because a proper SSO solution can be more secure (2FA) and streamlined.