title: Passing an input to a service and saving the result to DB in Django
body: <p>I have a Django application that involves a model with five fields. In the case of one of these fields, I want users to enter a bunch of text, which I then want to submit to a service (via a function call) and save the result. To provide a visual representation:</p>
  
  <p><a href="https://i.stack.imgur.com/1cnuR.png" rel="noreferrer"><img src="https://i.stack.imgur.com/1cnuR.png" alt="enter image description here"></a></p>
  
  <p>How does one best play this? One option to me would be to override the save() function, but the types are different - I want the form to show a models.TextField field but save it as the results of a URLField would be saved. Equally, when displayed, I want the user to edit not the URL but rather the text retrieved from that URL.</p>