Is generally aligned with out SAML2 group sync functionality, but for
OIDC based upon feedback in #3004.
Neeeded the tangental addition of being able to define custom scopes on
the initial auth request as some systems use this to provide additional
id token claims such as groups.
Includes tests to cover.
Tested live using Okta.
- Made oidc config more generic to not be overly reliant on the library
based upon learnings from saml2 auth.
- Removed any settings that are redundant or not deemed required for
initial implementation.
- Reduced some methods down where not needed.
- Renamed OpenID to OIDC
- Updated .env.example.complete to align with all options and their
defaults
Related to #2169
