OAuth2 Single Sign-On (SSO) with the new OAuth 2.0 Login module

@hngondoki what’s your use case?

Also note that the README promises something that’s not yet implemented about the initial set of roles to give to users when they are being created (see here). Not a big deal to run the last mile though. However somehow we never had to prioritise it. I detailed it here already: GSoC 2020: Advancement of OAuth2 Module and Improvements in SMART OWA