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Use case

In order to facilitate the migration from the old Google Sign In SDK to the Google Identity Services SDK, the signIn method of the google_sign_in_web plugin attempted to both authenticate and authorize users and return both tokens.

The way this worked was by using the oauth2 authorization process, and then doing a request to the People API to retrieve information about me (the currently signed-in user). This didn't return a proper idToken (authentication) so the method wasn't really usable by users.

Proposal

Remove the signIn method from the web implementation of google_sign_in, so it starts throwing an UnimplementedException, now that users have migrated to the new Card / SDK Button method.

Remove all the accessory code that was used to attempt to retrieve the information about the currently signed-in user, like _computeUserDataForLastToken, _requestedUserData and any others.

Update the documentation to note that the plugin does not require access to the "People API" any longer.

Bump a major version on the plugin, so we need to update the core plugin (and its documentation) to release this deprecation to the public.