Tests are missing, let's ship it, I'll open an issue.
Without such protection, the whole app would crash if the resource server is
not configured. The fallback backend would return an appropriate error to
the client if the resource server is improperly configured.
Overload mozilla-django-oidc class to support an authentication method
with the resource server backend.
This enables any route of the API to be called with an access token
issued by Agent Connect.