SSO/OAuth support for OPDS

[WirtsLegs]

OPDS v2 doesnt seem to have a spec for OAuth though they are working on it, however it seems there is a spec for how to accomplish OAuth support with OPDS v1 here

Adding this support would allow disabling local passwords and entirely move to the SSO provider.

[gotson]

I already discussed with the OPDS folks, until they get their spec sorted there's nothing i can do.