title: How to authenticate user with just a Google account on Actions on Google?
body: <p>Currently Google Assitant includes an easy way <a href="https://stackoverflow.com/questions/44287115/difference-betwee-googleuser-getid-oauth-vs-app-getuser-userid-action/44288268#44288268">to request non-identifiable information about the user</a> and a detailed flow to authenticate the user on a third party service through OAuth2. What about if all I need is have the user authenticate on Google itself? I tried filling in the account linking flow using Google OAuth2 information, but that seems not to work. If that last thing is supposed to work fluently than that would be enough of an answer.</p>
  
  <p>Context: Users already authenticate only with Google on a related webpage. All I need is to link this already authenticated account with the less-authenticated account on Google Assistant.</p>