Which of the Google Play Services APIs are minimally required for authenticating through Firebase in a Flutter app?

Question

Firebase in the docs for flutter says one should put the whole of google services into the dependencies.

dependencies {
        // ...
        classpath 'com.google.gms:google-services:3.2.1'   // new
}

As others suggested ( https://stackoverflow.com/a/39513236/5369792 ) this is not good practice as it bloats the app because it downloads all of the APIs. Most of which are unnecessary and and leading to requiring Multidex even for a minimal 'hello world' app with user login.

Google Play Services has many APIs as per https://developers.google.com/android/guides/setup They are all downloaded by the above dependency requirement merely because Firebase wants to read google services json file.

It would be much more efficient to add just a specific dependency that Firebase actually needs. So the question is which dependency(-ies) Firebase needs for a minimal user authentication and to just read the google services json file?