title: django auth: increasing max_length group name field
body: <p>In <code>Django 1.8</code> the <code>max_length</code> of <code>name</code> field for <code>Group</code> model in the <code>auth</code> app is by default <code>80</code> characters.</p>
  
  <p>I need to increase this limit without extending the default group model.</p>