Firebase功能+ Firestore +向多个令牌发送通知

Question

我创建了以下功能，用于将通知发送给特定的 fcmToken

/**
 * FOR ADMIN
 */
exports.adminNotification = functions.firestore.document('/pending_videos/{pushId}').onCreate(async (snap, context) => {

    const newValue = snap.data();
    const title = newValue.title;
    const category = newValue.category;
    const uploadedBy = newValue.uploadedBy;

    // Grab the current value of what was written to the Realtime Database.

    let adminRef = admin.firestore().collection('admin').doc('57MRzgiBwx2gO2JXZ4jo');
    let token;
    let getDoc = adminRef.get()
      .then(doc => {
        if (!doc.exists) {
          console.log('No such document!');
        } else {
            console.log('Document data:', doc.data().url);
            token = doc.data().token;

            // Create a notification
            const payload = {
                data: {
                    title: "Jain Stavan Video Status",
                    body:  title + " video uploaded in " + category + " category by " + uploadedBy + ".",
                    sound: "default"
                },
            };

            //Create an options object that contains the time to live for the notification and the priority
            const options = {
                priority: "high",
                timeToLive: 60 * 60 * 24
            };

            console.log('Sending notification');

            return admin.messaging().sendToDevice(token, payload, options);
        }
      })
      .catch(err => {
        console.log('Error getting document', err);
      });
});

我已经使用静态文档 .doc（'57MRzgiBwx2gO2JXZ4jo'）完成了此操作，但我想将其发送给所有 admin ，这意味着 admin中的所有文档收藏。

我该怎么做？