Send FCM push message as labeled data messages, so they show up in Firebase Cloud Messaging Reports

Description:

As of 3.6.3, FCM push notifications are sent without analytics label, meaning they don't show up in Firebase Cloud Reports.
Propose to add (meaningful) analytics labels, so they show up in Firebase Cloud Reports, for analytics purpose or for troubleshooting/diagnostics purposes.

Reference: https://firebase.google.com/docs/cloud-messaging/understand-delivery?authuser=0#adding_analytics_labels_to_messages

Steps to reproduce:

1. Ensure you set your own FCM account
2. Sign in with Android mobile app
3. Close the app (make it in background)
4. Send a message from another user
5. Notice that push notification is received
6. Go to Firebase Cloud Reports

Expected behavior:

You get 1 data point, with at least 1 Send and 1 Receive, and probably 1 Impression and 1 Open.

Actual behavior:

No data:

Server Setup Information:

• Version of Rocket.Chat Server: 3.6.3
• Operating System: linux x64 4.14.193-149.317.amzn2.x86_64
• Deployment Method: AWS Fargate (Docker)
• Number of Running Instances: 1
• DB Replicaset Oplog: local
• NodeJS Version: 12.6.1
• MongoDB Version: 4.2.9

Client Setup Information

• Desktop App or Browser Version: Rocket.Chat.ReactNative for Android 4.10.0
• Operating System: Android 10

Additional context

Relevant logs:

I20200929-11:57:30.171(0) server.js:204 Push ➔ debug sendGCM [   'fkhBWgHdTBS...RLX-k6' ] {   createdAt: 2020-09-29T11:57:30.162Z,   createdBy: '<SERVER>',   sent: false,   sending: 0,   from: 'push',   title: '#ATG-test',   text: 'hendy: Cek',   userId: 'RejdvL7N9tgtAhHHs',   payload: {     host: 'https://chat.soluvas.com/',     messageId: 'YR2ITYBVY2XaVI2VR',     notificationType: 'message',     rid: 'SAPhPv73kzD7c5vY3',     sender: { _id: 'WF888NBfytPJMnuu2', username: 'hendy' },     type: 'p',     name: 'ATG-test'   },   badge: 2,   sound: 'default',   notId: 1633641473,   apn: { category: 'MESSAGE' },   gcm: {     image: 'https://chat.soluvas.com/images/logo/android-chrome-192x192.png',     style: 'inbox'   },   image: 'https://chat.soluvas.com/images/logo/android-chrome-192x192.png',   style: 'inbox' } 

The issue names no implementation file or test. Start with the referenced Firebase Cloud Messaging analytics-label documentation, then locate the React Native FCM message-sending entry point and verify the change by checking that sent notifications produce data in Firebase Cloud Reports.