Метод didUpdate не вызывается в первый раз при реализации push-уведомлений VOIP с использованием pushkit

Question

Я могу отправить VOIP push-уведомление, используя следующий код:

    @UIApplicationMain
    class AppDelegate: UIResponder, UIApplicationDelegate,PKPushRegistryDelegate {


    var window: UIWindow?
    var isUserHasLoggedInWithApp: Bool = true
    var checkForIncomingCall: Bool = true
    var userIsHolding: Bool = true

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {


        if #available(iOS 8.0, *){


            let viewAccept = UIMutableUserNotificationAction()
            viewAccept.identifier = "VIEW_ACCEPT"
            viewAccept.title = "Accept"
            viewAccept.activationMode = .foreground
            viewAccept.isDestructive = false
            viewAccept.isAuthenticationRequired =  false

            let viewDecline = UIMutableUserNotificationAction()
            viewDecline.identifier = "VIEW_DECLINE"
            viewDecline.title = "Decline"
            viewDecline.activationMode = .background
            viewDecline.isDestructive = true
            viewDecline.isAuthenticationRequired = false

            let INCOMINGCALL_CATEGORY = UIMutableUserNotificationCategory()
            INCOMINGCALL_CATEGORY.identifier = "INCOMINGCALL_CATEGORY"
            INCOMINGCALL_CATEGORY.setActions([viewAccept,viewDecline], for: .default)

            if application.responds(to: #selector(getter: UIApplication.isRegisteredForRemoteNotifications))
            {
                let categories = NSSet(array: [INCOMINGCALL_CATEGORY])
                let types:UIUserNotificationType = ([.alert, .sound, .badge])

                let settings:UIUserNotificationSettings = UIUserNotificationSettings(types: types, categories: categories as? Set<UIUserNotificationCategory>)

                application.registerUserNotificationSettings(settings)
                application.registerForRemoteNotifications()
            }

        }
        else{
            let types: UIRemoteNotificationType = [.alert, .badge, .sound]
            application.registerForRemoteNotifications(matching: types)
        }


        self.PushKitRegistration()

        return true
    }

    //MARK: - PushKitRegistration

    func PushKitRegistration()
    {

        let mainQueue = DispatchQueue.main
        // Create a push registry object
        if #available(iOS 8.0, *) {

            print("here1")

            let voipRegistry: PKPushRegistry = PKPushRegistry(queue: mainQueue)

            // Set the registry's delegate to self

            voipRegistry.delegate = self
            // Set the push type to VoIP
            voipRegistry.desiredPushTypes = [PKPushType.voIP]

        } else {
            // Fallback on earlier versions
        }


    }

    @available(iOS 8.0, *)
    func pushRegistry(_ registry: PKPushRegistry, didUpdate credentials: PKPushCredentials, forType type: PKPushType) {
        // Register VoIP push token (a property of PKPushCredentials) with server
        print("during registration ")
        //print(credentials.token)

        // Swift 2 format
        //        let hexString : String = UnsafeBufferPointer<UInt8>(start: UnsafePointer(credentials.token.bytes),
        //                                                            count: credentials.token.length).map { String(format: "%02x", $0) }.joinWithSeparator("")

        // Swift 4 format

        let token = credentials.token.map { String(format: "%02x", $0) }.joined()
        print(token)

    }
    func pushRegistry(_ registry: PKPushRegistry, didReceiveIncomingPushWith payload: PKPushPayload, for type: PKPushType, completion: @escaping () -> Void) {
        print("incomming push escaping")
    }
    func pushRegistry(_ registry: PKPushRegistry, didInvalidatePushTokenForType type: PKPushType) {
        print("invalid")
    }
    @available(iOS 8.0, *)

    func pushRegistry(_ registry: PKPushRegistry, didReceiveIncomingPushWith payload: PKPushPayload, forType type: PKPushType) {

        print("incoming push")
        // Process the received push

        // Below process is specific to schedule local notification once pushkit payload received

        var arrTemp = [AnyHashable: Any]()
        arrTemp = payload.dictionaryPayload

        let dict : Dictionary <String, AnyObject> = arrTemp["aps"] as! Dictionary<String, AnyObject>


        if isUserHasLoggedInWithApp // Check this flag then only proceed
        {

            if UIApplication.shared.applicationState == UIApplicationState.background || UIApplication.shared.applicationState == UIApplicationState.inactive
            {

                if checkForIncomingCall // Check this flag to know incoming call or something else
                {

                    var strTitle : String = dict["alertTitle"] as? String ?? ""
                    let strBody : String = dict["alertBody"] as? String ?? ""
                    strTitle = strTitle + "\n" + strBody

                    let notificationIncomingCall = UILocalNotification()

                    notificationIncomingCall.fireDate = Date(timeIntervalSinceNow: 1)
                    notificationIncomingCall.alertBody =  strTitle
                    notificationIncomingCall.alertAction = "Open"
                    notificationIncomingCall.soundName = "SoundFile.mp3"
                    notificationIncomingCall.category = dict["category"] as? String ?? ""

                    //"As per payload you receive"
                    notificationIncomingCall.userInfo = ["key1": "Value1"  ,"key2": "Value2" ]

                    UIApplication.shared.scheduleLocalNotification(notificationIncomingCall)

                }
                else
                {
                    //  something else
                }

            }
        }
    }

}

Но учетные данные didUpdate: PKPushCredentials не вызывается в первый раз. В консоли есть push-ключ для печати токена устройства. Но я не знаю, откуда он печатает токен устройства.

Итак, я не могу хранить этот токен устройства. Если я запускаю это приложение второй раз, не удаляя предыдущее, вызывается метод didUpdate. Как я могу получить токен устройства при первом запуске приложения, чтобы я мог сохранить этот токен в UserDefaults?