Auth
- Added Anonymous Login as a provider (#505)
- Added account management callbacks (#510)
- Added one-time autofill support on iOS 12 (#516)
- Fixed auto-upgrade of anonymous accounts not correctly invoking callbacks in some cases (#504, #512, #518, #519)
- Added anonymous auth upgrade docs to FirebaseAuthUI readme (#522)
Database
- Improved error reporting for internal state inconsistencies in FUIArray (#523)