Some providers like Auth0 and Okta has this /userinfo endpoint that you can send a GET request with the access token and get the data of the user stored in the server.

It could be nice to implement this using the subjects we create when setting up the issuer server, fetch /userinfo and get the subject data back.

I know the subject is included in the access token JWT but supporting this would allow OpenAuth to be more generic as a resource server receiving the access token can fetch the /userinfo endpoint regardless if the IdP is OpenAuth, Auth0, Okta, etc.