Add support for RFC 7628 openid-configuration element in SASL reply. This would simplify adding any 3rd party oauth provider to #thunderbird and allow migrating from password authentication.
The server side of this is implemented i e.g. Dovecot IMAP server, see https://doc.dovecot.org/configuration_manual/authentication/oauth2/#openid-discovery .
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That request has been in the system for some years now.