I\'m newbie to Firestore. Firestore docs says...
Important: Unlike \"push IDs\" in the Firebase Realtime Database, Cloud Firestore au
Use firestore Timestamp class, firebase.firestore.Timestamp.now().
firebase.firestore.Timestamp.now()
Since firebase.firestore.FieldValue.serverTimestamp() does not work with add method from firestore. Reference
firebase.firestore.FieldValue.serverTimestamp()
add