FCM: Handling of NotRegistered errors about mod_push_appserver HOT 1 CLOSED

      async componentDidMount() {
        this.checkPermission();
        this.createNotificationListeners();
      }

  async checkPermission() {
    const enabled = await firebase.messaging().hasPermission();
    if (enabled) {
      this.getToken();
    } else {
      this.requestPermission();
    }
  }

  async requestPermission() {
    try {
      await firebase.messaging().requestPermission();
      // User has authorised
      this.getToken();
    } catch (error) {
      // User has rejected permissions
      console.log('permission rejected');
    }
  }

  async getToken() {
    try {
      const enabled = await firebase.messaging().hasPermission();
      if (!enabled) {
        await firebase.messaging().requestPermission();
      }

      const fcmToken = await firebase.messaging().getToken();
      if (fcmToken) {
        console.log("got token");
        console.log('fcm token:', fcmToken); //-->use this token from the console to send a post request via postman
        this.setState({ fcmToken });
        return fcmToken;
      }
    } catch (error) {
      console.warn('notification token error', error);
    }
  }

 async createNotificationListeners() {
    /*
    * Triggered when a particular notification has been received in foreground
    * */
    this.notificationListener = firebase.notifications().onNotification((notification) => {
        const { title, body } = notification;
        this.showAlert(title, body);
    });
  
    /*
    * If your app is in background, you can listen for when a notification is clicked / tapped / opened as follows:
    * */
    this.notificationOpenedListener = firebase.notifications().onNotificationOpened((notificationOpen) => {
        const { title, body } = notificationOpen.notification;
        this.showAlert(title, body);
    });
  
    /*
    * If your app is closed, you can check if it was opened by a notification being clicked / tapped / opened as follows:
    * */
    const notificationOpen = await firebase.notifications().getInitialNotification();
    if (notificationOpen) {
        const { title, body } = notificationOpen.notification;
        this.showAlert(title, body);
    }
    /*
    * Triggered for data only payload in foreground
    * */
    this.messageListener = firebase.messaging().onMessage((message) => {
      //process data message
      console.log(JSON.stringify(message));
    });
  }