Add Google Oauth2 authenticator. The current Google OpenID authentication has been deprecated by Google and will NOT work for any new websites.

app/controllers/users/omniauth_callbacks_controller.rb

@@ -8,6 +8,7 @@ class Users::OmniauthCallbacksController < ApplicationController
   BUILTIN_AUTH = [
     Auth::FacebookAuthenticator.new,
     Auth::OpenIdAuthenticator.new("google", "https://www.google.com/accounts/o8/id", trusted: true),
+    Auth::GoogleOAuth2Authenticator.new,
     Auth::OpenIdAuthenticator.new("yahoo", "https://me.yahoo.com", trusted: true),
     Auth::GithubAuthenticator.new,
     Auth::TwitterAuthenticator.new