[Plugin OIDC OP] Addition in Confluence Documentation, so that OIDC Configuration can be retrieved

[Cantor, Scott]

> Otherwise, the openid configuration under /idp/profile/oidc/configuration
> cannot be retrieved and the documentation above is a bit misleading.

I don't think we really see client registration as a "core" feature so it isn't part of any quick-start material, it's covered *if* you want to actually support that feature. That's why the follow on section talks about just mocking up some metadata for testing.

Client registration requires a database and I would never advocate that anybody deploy a database with their IdP. There are a half dozen other problems with the approach that make it a trap for anybody so not the sort of thing I would ever encourage in the introductory material.

-- Scott