UserDataProvider.dart

  @override
  Future<void> updateProfilePicture(String profilePictureUrl) async {
    String uid = SharedObjects.prefs.getString(Constants.sessionUid);
    DocumentReference ref = fireStoreDb.collection(Paths.usersPath).document(
        uid); //reference of the user's document node in database/users. This node is created using uid
    var data = {
      'photoUrl': profilePictureUrl,
    };
    await ref.setData(data, merge: true); // set the photourl
  }