feat(adapters): move to `firebase-admin` in Firebase Adapter (#6225)
Co-authored-by: Balázs Orbán <info@balazsorban.com>
fixes https://github.com/nextauthjs/next-auth/issues/5049
closes https://github.com/nextauthjs/next-auth/pull/6230
closes https://github.com/nextauthjs/next-auth/pull/5449
closes https://github.com/nextauthjs/next-auth/pull/5055
fixes https://github.com/nextauthjs/next-auth/issues/4927
BREAKING CHANGE:
The adapter now expects `firebase-admin` instead of the `firebase` package and also supports either passing a config object or a firestore instance.