https://cloud.google.com/v1/oauth/authorize?response_type=code&client_id=CLIENT_ID&redirect_uri=CALLBACK_URL&scope=USER INFO
App-server
oauth-server
4.passing code to server end
2.send in request
10.User Login to APP
7.access_token
App GUI
8.access_token
3. login from google and code is sent to CALLBACK_URL
6.access_token+refresh_token
access app GUI
9.come back with the USER_INFO
resource-server
5.using code to request for access token e.g. JWT
