GAccount Class that holds the account information of the signed in Google user.
 GRest This class will help you with more activities you can do with Google Auth API.
 GRestTokens On a successful operation on method, an instance of this class will be returned which will hold the tokens.
 GScopes Learn more about GoogleScopes here:
 GSignIn Entry point for the Google Sign In API.
 GSignInOptions GSignInOptions is options used to configure the default GSignin behaviour.