title: Django FileField() disable upload
body: <p>I have a <code>FileField()</code> in a Django model. On <code>save()</code>, I intercept this and upload the actual file data to a remote-backend/Bucket, then save the URL returned from the service in another field.</p>
  
  <p>The file actually uploads to my file-system (I believe).</p>
  
  <p><strong>How can I disable the <code>FileField()</code> to not actually upload the file to wherever media is stored with Django?</strong></p>