title: User Model fields not showing in Django Admin Panel
body: <p>I have a basic model that extends the User model:</p>
  
  <pre><code>from django.contrib.auth.models import User
  
  class Promotion (models.Model):
      User = models.ForeignKey(User)
      Rating = models.ForeignKey(Rating)
      Date_Effective = models.DateField()
  
      def __str__(self):
          return self.Rating.Rank.Short_Rank + ' ' + self.User.last_name + ' (' + str(self.Date_Effective) + ')'
  </code></pre>
  
  <p>in my Admin.py, i have the models showing:</p>
  
  <pre><code>admin.site.register(models.Promotion)
  </code></pre>
  
  <p>when loading a promotion, the <code>Short_Rank</code> field and the <code>Date_Effective</code> fields show perfectly, but the <code>User.last_name</code> does not.</p>
  
  <pre><code>ADM (2017-03-18)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/PVb04.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PVb04.png" alt="enter image description here"></a></p>
  
  <p>This is consistent with the rest of the models, and I am believing that the User model itself is not being attacked by the query in the admin panel.  How do I get the name fields in the User model showing in the model page of the Admin panel?  Thanks.</p>