title: Azure B2C Setting a Customer Policy with auto generated Username for Signup
body: <p>So I am trying out Azure B2C to see what the pros / cons are of the service.</p>
  
  <p>Basically as a use case I want users to sign up with their email address but have an auto generated username that they will use to sign in.</p>
  
  <p>I have set the local signin to use username so sign in works correctly. But during the signup process the username field appears and allows the user to input a desired username.</p>
  
  <p>Is there a way, perhaps through custom policies, to automatically set the username field to a value (incremented from user ids column) and not allow the user to update this value?</p>
  
  <p>Thanks in advance!</p>