push registration no longer depends on notification permission, reporting effective opt-in and os permission

lib/push/push_status.dart

@@ -1,4 +1,3 @@
-import 'package:firebase_messaging/firebase_messaging.dart';
 import 'package:flutter/foundation.dart';
 
 import '../model/account_data.dart';
@@ -141,21 +140,11 @@ Future<PushStatusReport> collectPushStatus({
 }
 
 Future<PushCheck> _osPermission() async {
-  try {
-    final settings = await FirebaseMessaging.instance.getNotificationSettings();
-    switch (settings.authorizationStatus) {
-      case AuthorizationStatus.authorized:
-      case AuthorizationStatus.provisional:
-        return PushCheck.ok;
-      case AuthorizationStatus.denied:
-      case AuthorizationStatus.deniedPermanently:
-        return PushCheck.fail;
-      case AuthorizationStatus.notDetermined:
-        return PushCheck.unknown;
-    }
-  } on Object {
-    return PushCheck.unknown;
-  }
+  final status = await PushRegistration.osPermissionStatus();
+  if (status == null) return PushCheck.unknown;
+  if (PushRegistration.canDisplay(status)) return PushCheck.ok;
+  if (!PushRegistration.isPermissionUsable(status)) return PushCheck.fail;
+  return PushCheck.unknown;
 }
 
 /// One line in the status checklist.