Not ready just yet, but technically we're at least at the point where we can talk planning.
Checklist per this:
- T174753: Create Help:Extension:GlobalPreferences on mw.org
- T184643: Security review for GlobalPreferences
- T184666: DBA review for GlobalPreferences schema
- T184668: Deploy GlobalPreferences on beta cluster
- T187488: Invite people to try out GlobalPreferences on the beta cluster and give feedback and any blocking bugs
- T189806: Deploy GlobalPrefs on production