title: How to use credentials to access Google Cloud information for other users
body: <p>I've been crawling the web but haven't been able to figure this out.</p>
  
  <p>I want to write an app with the following behavior: it presents existing users of Google Cloud with a login window to which they enter their Cloud credentials - user and password. With those credentials, I want to programmatically access and fetch their respective billing data so I can later display it to them. This should obviously be able to serve multiple users.</p>
  
  <p>I don't understand how to get past the very first step, which is - what do I do after I get the credentials? Is there a client library method to which I supply them and then gain access to the user's info?</p>