iOS Push Notification Notes
UIApplication https://developer.apple.com/documentation/uikit/uiapplication/ registerForRemoteNotifications() https://developer.apple.com/documentation/uikit/uiapplication/1623078-registerforremotenotifications If registration succeeds, the app calls your app delegate object’s application(_:didRegisterForRemoteNotificationsWithDeviceToken:) method and passes it a device token.