Certified OpenID Connect authentication flow

[CorentinDeBoisset]

More and more services are starting to conform to the OpenID Connect standard (Keycloak, Google, Microsoft 365, Linkedin, Gitlab or Nextcloud for instance), and the custom-made implementation in Rocketchat is not fully compliant. The maintenance of this layer feels out-of-scope for this project, maybe a well maintained and compliant library could be used instead?

See here: https://openid.net/developers/certified-openid-connect-implementations/

OIDC is based on OAuth 2.0, so the workflows should stay close to what is already existing in RocketChat. See more information here: https://openid.net/developers/how-connect-works/

If you want, I can make a proof of concept but since it affects the product features, a preliminary discussion seems adequate.