Implemented structure for push Notifications

lib/notification/notificationController.dart

@@ -0,0 +1,45 @@
+import 'dart:developer';
+
+import 'package:firebase_core/firebase_core.dart';
+import 'package:firebase_messaging/firebase_messaging.dart';
+import 'package:flutter/cupertino.dart';
+
+import '../api/marianumcloud/talk/room/getRoom.dart';
+import '../api/marianumcloud/talk/room/getRoomParams.dart';
+import '../model/accountData.dart';
+import 'notificationService.dart';
+
+class NotificationController {
+  @pragma('vm:entry-point')
+  static Future<void> onBackgroundMessageHandler(RemoteMessage message) async {
+    log("Handling a background notification: ${message.messageId}");
+
+    await Firebase.initializeApp();
+    AccountData().waitForPopulation().then((value) {
+      log("User account status: $value");
+      if(value) {
+        GetRoom(
+          GetRoomParams(
+            includeStatus: false,
+          ),
+        ).run().then((value) {
+          var messageCount = value.data.map((e) => e.unreadMessages).reduce((a, b) => a + b);
+          var chatCount = value.data.map((e) => e.unreadMessages).length;
+          var people = value.data.where((e) => e.unreadMessages > 0).map((e) => e.displayName.split(" ")[0]);
+
+          final NotificationService service = NotificationService();
+          service.initializeNotifications().then((value) {
+            service.showNotification(
+                title: "Du hast $messageCount ungelesene Nachrichten!",
+                body: "In $chatCount Chats, von ${people.join(", ")}"
+            );
+          });
+        });
+      }
+    });
+  }
+
+  static Future<void> onForegroundMessageHandler(RemoteMessage message, BuildContext context) async {
+    NotificationService().showToast(message: "Du hast eine neue Talk Nachricht!", context: context);
+  }
+}