frontend: Add auth mechanism to call GOB API directly from UI

As outlined in the design doc, in order to be able to make authenticated API call to GOB we need to get the oauth token from GOB. To do that, we can

• Render an empty iframe, which loads GOB oauth flow and stores the auth token
• Wait for the auth flow to complete, and handle any error, timeout
• Make it as a reusable component, so that it can be reused in any page that needs to talk to GOB
• Query API on GOB directly using {withCredentials: true}