OAuth2 introspection endpoint
Summary
The purpose of the feture request is to implement a OAuth2 introspection endpoint, to be able to validate access token without requesting userinfo endpoint.
Design proposition
Implementation should follow the RFC 7662 : https://tools.ietf.org/html/rfc7662 OIDC metadata (.https://OAUTH2_SERVER/.well-known/openid-configuration) file should also be completed with introspection_endpoint according to the RFC8414 : https://tools.ietf.org/html/rfc8414