Optional+Require.swift

    //This function is called when you successfully registered for remote notifs
    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        
        //This is one way we can convert the device token data into a String.  
        //apns stands for Apple Push Notification Services
        let apnsDeviceToken = deviceToken.map {String(format: "%02.2hhx", $0)}.joined()
        print(apnsDeviceToken)
    }