Build issue after flutter upgrade

[msandwidi]

Hello everyone and thank you for keeping this package up to date.

I recently upgraded flutter in one of my projects that uses this package but the build is now breaking with the following message.

E/GeneratedPluginRegistrant(17354): 	at io.flutter.embedding.engine.plugins.util.GeneratedPluginRegister.registerGeneratedPlugins(GeneratedPluginRegister.java:80)
E/GeneratedPluginRegistrant(17354): 	at io.flutter.embedding.engine.FlutterEngine.<init>(FlutterEngine.java:355)
E/GeneratedPluginRegistrant(17354): 	at io.flutter.embedding.engine.FlutterEngine.<init>(FlutterEngine.java:263)
E/GeneratedPluginRegistrant(17354): 	at io.flutter.embedding.engine.FlutterEngine.<init>(FlutterEngine.java:243)
E/GeneratedPluginRegistrant(17354): 	at io.flutter.embedding.engine.FlutterEngine.<init>(FlutterEngine.java:163)
E/GeneratedPluginRegistrant(17354): 	at io.flutter.plugins.firebase.messaging.FlutterFirebaseMessagingBackgroundExecutor.lambda$startBackgroundIsolate$0$FlutterFirebaseMessagingBackgroundExecutor(FlutterFirebaseMessagingBackgroundExecutor.java:167)
E/GeneratedPluginRegistrant(17354): 	at io.flutter.plugins.firebase.messaging.-$$Lambda$FlutterFirebaseMessagingBackgroundExecutor$XbAhdPvj3YfytSw4YC4mSEzUFHw.run(Unknown Source:8)
E/GeneratedPluginRegistrant(17354): 	at android.os.Handler.handleCallback(Handler.java:883)
E/GeneratedPluginRegistrant(17354): 	at android.os.Handler.dispatchMessage(Handler.java:100)
E/GeneratedPluginRegistrant(17354): 	at android.os.Looper.loop(Looper.java:214)
E/GeneratedPluginRegistrant(17354): 	at android.app.ActivityThread.main(ActivityThread.java:7356)
E/GeneratedPluginRegistrant(17354): 	at java.lang.reflect.Method.invoke(Native Method)
E/GeneratedPluginRegistrant(17354): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
E/GeneratedPluginRegistrant(17354): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

The issue may be arising because the PluginRegistry.Registrar is deprecated. We might want to upgrade it it support the new Android APIs. I have seen the upgrade steps here https://docs.flutter.dev/development/packages-and-plugins/plugin-api-migration but I have no experience working with plugins.

Any help fixing this issue will be much appreciated. Thank you again