feat(messaging): android.tag property on Notification (#5452)

Author: russellwheatley

packages/firebase_messaging/firebase_messaging/android/src/main/java/io/flutter/plugins/firebase/messaging/FlutterFirebaseMessagingUtils.java

@@ -149,6 +149,10 @@ private static Map<String, Object> remoteMessageNotificationToMap(
       androidNotificationMap.put("visibility", notification.getVisibility());
     }
 
+    if (notification.getTag() != null) {
+      androidNotificationMap.put("tag", notification.getTag());
+    }
+
     notificationMap.put("android", androidNotificationMap);
     return notificationMap;
   }

packages/firebase_messaging/firebase_messaging/example/lib/main.dart

@@ -127,7 +127,6 @@ class _Application extends State<Application> {
     FirebaseMessaging.onMessage.listen((RemoteMessage message) {
       RemoteNotification notification = message.notification;
       AndroidNotification android = message.notification?.android;
-
       if (notification != null && android != null) {
         flutterLocalNotificationsPlugin.show(
             notification.hashCode,

packages/firebase_messaging/firebase_messaging_platform_interface/lib/src/remote_notification.dart

@@ -39,6 +39,7 @@ class RemoteNotification {
         smallIcon: map['android']['smallIcon'],
         sound: map['android']['sound'],
         ticker: map['android']['ticker'],
+        tag: map['android']['tag'],
         visibility: convertToAndroidNotificationVisibility(
             map['android']['visibility']),
       );
@@ -112,6 +113,7 @@ class AndroidNotification {
       this.smallIcon,
       this.sound,
       this.ticker,
+      this.tag,
       this.visibility = AndroidNotificationVisibility.private});
 
   /// The channel the notification is delivered on.
@@ -153,6 +155,9 @@ class AndroidNotification {
 
   /// The visibility level of the notification.
   final AndroidNotificationVisibility visibility;
+
+  /// The tag of the notification.
+  final String? tag;
 }
 
 /// Apple specific properties of a [RemoteNotification].