Supporting XOAUTH2 authentication mechanism

[francescobianco]

Starting February 15, 2021, G Suite accounts will only allow access to apps using OAuth
google/gmail-oauth2-tools#18

cc @dhedberg Any luck to have this over the official PHP release?

@senseisimple

[dhedberg]

We ended up not needing this, so I think it's stuck for now unless someone else helps it over the finish line.

There's also no proper upstream for this library as far as I can tell, so I guess the patch would have to be adopted separately by Debian and any other distributions that still carry it, if any.

Which also raises the question whether it's a good idea to add features and keep relying on it in the first place..

[Uzume]

The Alpine email client fork of UW IMAP contains this support since 2.22 (initial support checked in on 2019-05-04). See imap/src/c-client/auth_oa2.c and Help for Alpine - XOAUTH2