OIDC: Client registration with OP

[kerryarchibald]

Client implementation guide

Does client have a static client_id for the OP?

Allow configuration of statically registered clients in EW config

AC:

• Add an optional entry to EW config staticOidcClients with { [issuer]: client_id } (see hydrogen implementation)
• when a static_id exists for the issuer, continue to attempt OIDC auth
• when no static_id exists continue to attempt dynamic client registration