Add oidc support

Closes #159 (closed)

This is rather wonky. We could:

• Ditch the current approach entirely and built a more custom view/models that support what we really want. Adding OIDC in the database, instead of settings.
• Refactor what we have Done
• Contribute upstream to dj rest auth

There is no image used for OIDC - @james.kiger please make the frontend either omit the image or use something generic related to OIDC.

For testing - please test with an existing non-oidc provider as well to ensure we didn't add regressions.