title: How to make a field editable=False in DRF
body: <p>I've a serializer. I want to restrict updating a field. How would I do that?</p>
  
  <pre><code>class ABCSerializer(serializers.ModelSerializer):
      class Meta:
          """Meta."""
  
          model = ModelA
          fields = ('colA', 'colB', 'colC',)
  </code></pre>
  
  <p><code>colA</code> is a required field while creating the object. However, it should not be allowed to update. How can I do that??</p>