Refactor registerPushNotificationHandlers

The function is now part of the Talk object. This helps make it clear
which package the function belongs to.

Author: vickz84259

examples/push_notifications/lib/main.dart

@@ -9,7 +9,7 @@ Future<void> main() async {
     options: DefaultFirebaseOptions.currentPlatform,
   );
 
-  await registerPushNotificationHandlers(
+  await Talk.registerPushNotificationHandlers(
     androidChannel: const AndroidChannel(
       channelId: 'com.talkjs.flutter_push_example.messages',
       channelName: 'Messages',

lib/talkjs_flutter.dart

@@ -32,14 +32,14 @@ class Talk {
     final hash = digest.toString().toLowerCase();
     return hash.substring(0, 20);
   }
-}
 
-Future<void> registerPushNotificationHandlers({AndroidChannel? androidChannel, IOSPermissions? iosPermissions}) async {
-  if ((Platform.isAndroid) && (androidChannel != null)) {
-    await registerAndroidPushNotificationHandlers(androidChannel);
-  }
+  static Future<void> registerPushNotificationHandlers({AndroidChannel? androidChannel, IOSPermissions? iosPermissions}) async {
+    if ((Platform.isAndroid) && (androidChannel != null)) {
+      await registerAndroidPushNotificationHandlers(androidChannel);
+    }
 
-  if ((Platform.isIOS) && (iosPermissions != null)) {
-    await registerIOSPushNotificationHandlers(iosPermissions);
+    if ((Platform.isIOS) && (iosPermissions != null)) {
+      await registerIOSPushNotificationHandlers(iosPermissions);
+    }
   }
 }