refactor[UP]: refactor pushHelper

Author: baltevl

lib/utils/background_push.dart

@@ -81,7 +81,7 @@ class BackgroundPush {
       );
       Logs().v('Flutter Local Notifications initialized');
       firebase?.setListeners(
-        onMessage: (message) => pushHelper(
+        onMessage: (message) => PushHelper.pushHelper(
           PushNotification.fromJson(
             Map<String, dynamic>.from(message['data'] ?? message),
           ),
@@ -477,7 +477,7 @@ class BackgroundPush {
     );
     // UP may strip the devices list
     data['devices'] ??= [];
-    await pushHelper(
+    await PushHelper.pushHelper(
       PushNotification.fromJson(data),
       clients: clients,
       instance: instance,