title: get current user for 'created_by' field in model class
body: <p>I'm currently working on a Django app, and I'm trying to set the current user as default on a model, but it doesn't work. </p>
  
  <pre><code>created_by = models.ForeignKey(User, default=request.user, null=True, blank=True, on_delete=models.DO_NOTHING, related_name='created_by')
  </code></pre>
  
  <p>I tried to override the save() method but it doesn't work either, anyone has any experience on this matter ?</p>
  
  <p>Thanks a lot in advance for your help</p>