title: Django admin model field set to current user
body: <p>I have a model with field:</p>
  
  <pre><code>class MyModel(models.Model):
      name = models.CharField(max_length=50)
      created_by = models.ForeignKeyField(User)
  </code></pre>
  
  <p>In my admin:</p>
  
  <pre><code>class MyModelAdmin(admin.ModelAdmin):
      list_display= ("name",)
      fields = ("name",)
  </code></pre>
  
  <p>Here I don't want <code>created_by</code> in admin while adding MyModel. I want it to be set to current user like <code>created_by = request.user</code></p>
  
  <p>How can I do this?</p>
  
  <p>Thank you</p>