Upgrade Firebase Google sign-in to Credential Manager SDK (current method deprecated)

[DiplomaticRobot]

Migrate Google sign-in integration to the new Credential Manager SDK as the current method is deprecated. Update Firebase Auth dependencies and authentication flow to use the officially supported approach.

References:

• https://firebase.google.com/docs/auth/android/google-signin
• https://developer.android.com/identity/sign-in/legacy-gsi-migration

[Mariano89]

+1, also tracking this on a fork

[DiplomaticRobot]

@Mariano89 you might consider interesting this expanded fork we've made for our production already live game Stepland (still not in all countries)
https://github.com/SomniGameStudios/godot-firebase-android

[Mariano89]

Thanks @DiplomaticRobot that's a really useful pointer. Your firestore layer in particular (native incrementBy/serverTimestamp sentinels + nested-map support) solves a couple of parity gaps I've been working around on my fork, so I'll likely cherry-pick from it.

One thing for anyone landing here from this issue: your fork is still on the legacy GoogleSignIn API too, so the Credential Manager migration this issue tracks is still open on both. Are you tracking that migration, or would you be open to a Credential Manager PR? Happy to collaborate on it since we're both maintaining descendants of the same base.

[DiplomaticRobot]

Thanks @Mariano89 for the appreciation of our fork, regarding the new CredentialManager this is a backlog work we need to do too, but as it was working for now its a nice to have until we develop/validate other aspects of the game, so yeah, we are more than welcome to accept PRs regarding this topic

feel free to contact me in discord by this id, so we can sync:

• sergames_indeed