[iid] FirebaseInstanceId.getId() method is not available in plugin

[talent-apps]

If a Firebase user uses multiple devices, there is a separate token for each one of his devices.
In order to identify the device, the following method needs to be available in the plugin:

FirebaseInstanceId.getId()

For more info, see:
https://stackoverflow.com/questions/44496966/how-to-handle-multiple-firebase-fcm-tokens-per-user

[ghost]

I have a pull request opened for this: #2328