[flutter_local_notifications] Add support for Android Tiramisu' `POST_NOTIFICATIONS` permission

[bartekpacia]

Implements two new methods on AndroidFlutterLocalNotificationsPlugin, requestPermission and isPermissionGranted, to let developers work with the new notification runtime permission added in Android 13 Tiramisu (API level 33)

Fixes #1597

[bartekpacia]

Locally Android integration tests pass when I use Flutter v3.0.5, but fail on Flutter v2.10.5.

[bartekpacia]

What's missing is returning a boolean result from requestPermission(). I'll implement this as well in this PR :)

[MaikuB]

Thanks for the PR, was going to comment that it looks like that was missing when it comes to dealing with the listener.

Also the the Java code from the isPermissionGranted method remains after you had removed the code on the Flutter/Dart side.

I'll take a closer look once the changes are done

[MaikuB]

Also just remembered about https://github.com/flutter/flutter/issues/12561 that can impact testing. A workaround is mentioned there

[bartekpacia]

@MaikuB Now AndroidFlutterLocalNotificationsPlugin.requestPermission() returns a Future<bool?> :)

[bartekpacia]

@MaikuB Thanks the for review, I'll make the changes soon :)

[MaikuB]

Thanks for making the change. I pushed a grammar fix for the error message you added in so I can try to merge sooner. One thing that this made me think about though is the ability to use the existing initialize() method to also request permissions too. This is something that's possible for iOS and macOS. I can try to look at that after this PR is merged

[bartekpacia]

Thank you for your help with getting this merged @MaikuB :)

Regarding your idea with requesting permissions on initialize(), you have the example app in mind, not the plugin itself, right?

[MaikuB]

No I'm referring to the plugin itself

[stephanie-finch]

Thanks both for working on this! 👏🏻

Weighing in from the product side for requesting on initialize(), it's often important to prompt the user for notif permissions at a very specific step in the new user flow to optimize conversion for accepting. So I'd wanna make sure the plugin doesn't automatically prompt users for permission in a way that isn't within our control.

[MaikuB]

If you look at how iOS/macOS works then there is control over that. This should be clearer if you look at the example app where it decides not to have permissions requested when calling initialize