title: Django: How to lock a Boolean field for futher updates once set to True?
body: <p>I'm wondering, I am managing a transition between two systems - and in one system I am using Django as the ORM and API backend.</p>
  
  <p>I have a field that I want to set to True, and once it is set to True, it stays True. Even if the update from the older legacy system wants it to be False.</p>
  
  <p>Is there a Django way to do this? Maybe overriding the <code>save()</code> method?</p>