title: Python Dash Basic Auth - get username in app
body: <p>I am currently making a Dash app which would show different layout based on user privilege, so I would like to be able to identify the user which is signed up. I'm using Basic Auth and I changed some lines in dash_auth/basic_auth.py:
  Original:</p>
  
  <pre><code>username_password_utf8 = username_password.decode('utf-8')
  username, password = username_password_utf8.split(':')
  </code></pre>
  
  <p>to:</p>
  
  <pre><code>username_password_utf8 = username_password.decode('utf-8')
  username, password = username_password_utf8.split(':')
  self._username = username
  </code></pre>
  
  <p>Unfortunately, I received the : AttributeError: 'BasicAuth' object has no attribute '_username' error when I tried to use the _username attribute from auth.</p>
  
  <pre><code>app.layout = html.Div(
      html.H3("Hello " + auth._username)
  )
  </code></pre>
  
  <p>I understand that the Dash app is already processed before authorization check, but I have no idea where to implement a callback that changes the layout according to username. How can I get the username in the Dash application?</p>