title: Amplify - How to setup congnito to use email as username?
body: <p>Using AWS Amplify to create an authentication (Cognito) with Reactjs, the default username is a UUID. So when I log in to the system I see: </p>
  
  <p>Hello f725e4a2-1f24-487d-9265-864947f5c5eb</p>
  
  <p>How do I change this behavior? There may be a way of changing this in the frontend, but I would like to change this in the backend, because the list of users in Cognito has UUIDs as the identifier as well. I would like to see email as username instead.</p>
  
  <p>Thank you!</p>