feat(oauth): add OIDC Discovery and RFC 8414 provider metadata endpoints

Andrew Evansrequested to merge
603629-oidc-discovery-endpoint into main

Adds /.well-known/openid-configuration and /.well-known/oauth-authorization-server endpoints. Most values are hard-coded to mirror gitlab-rails' endpoint served by Doorkeeper and JWKSController. We advertise capabilities where IAM Service doesn't yet support them, but Doorkeeper does. Capabilities that IAM supports but Doorkeeper does not are hidden for now.

We have one split between the two endpoints, as JWKSController does, to note the dynamic client registration endpoint for /.well-known/oauth-authorization-server .

Closes gitlab-org/gitlab#603629 (closed)

How to set up and validate locally

  1. Build this branch and run the service
  2. Visit http://localhost:8084/.well-known/openid-configuration
  3. Visit http://localhost:8084/.well-known/oauth-authorization-server
Edited by Andrew Evans

Merge request reports