Support Firebase Authentication emulator

[tzappia]

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Documentation changes
• Other... Please describe:

PR Checklist

Please check your PR fulfills the following requirements:

New features/enhancements:

• Exhaustive testing has been carried out for the new functionality
• Regression testing has been carried out to ensure no existing functionality is adversely affected
• Documentation has been added / updated
• The example project has been update to validate/demonstrate the new functionality.

What is the purpose of this PR?

This change adds support for the Firebase Authentication emulator which is part of the Firebase Local Emulator Suite. It allows authentication to be handled by a local emulator suite rather than a real Firebase project instance.

Does this PR introduce a breaking change?

• Yes
• No

What testing has been done on the changes in the PR?

This PR has been tested with the useAuthEmulator function called after the FirebasePlugin has been initialized. It successfully connects and uses the configured authentication emulator for Firebase Authentication operations.

What testing has been done on existing functionality?

This PR has been tested without calling the useAuthEmulator function. All existing Firebase Authentication behaviour is unchanged.

Other information

The changes in this PR have been used in a production app available on both the App Store and Google Play Store.