The MusicBrainz OAuth authentication is supposed to be migrated to a centralized MetaBrainz authentication.

As soon as the necessary infrastructure is available Picard should be prepared for the switch.

As discussed with bitmap it should be feasible to provide the necessary token request endpoint on musicbrainz.org for backward compatibility for existing versions. But we should still push users to upgrade and provide updated Picard versions (both for Picard 2.x and 3.x).