title: Add password to Django Group model
body: <p>Is it possible to password protect groups so that a user can only join a group if the user has a password for that group?</p>
  
  <p>I know it's possible to add fields to the Group model with</p>
  
  <p><code>Group.add_to_class('password', CharField(max_length=180, null=True, blank=True))</code></p>
  
  <p>But how can I implement this in a secure way? I want the password to be properly hashed and stored. In essence, how can I add the <code>User</code> password field to <code>Group</code> as well?</p>
  
  <p>EDIT:</p>
  
  <p>The docstring for the <code>Group</code> class in the source.</p>
  
  <blockquote>
    <p>Groups are a generic way of categorizing users to apply permissions,
    or some other label, to those users. A user can belong to any number
    of groups.</p>
    
    <p>Beyond permissions, groups are a convenient way to categorize users to
    apply some label, or extended functionality, to them.</p>
  </blockquote>
  
  <p>All I'm using a group for here is a label, and I want to password protect that label for when users try to join.</p>