title: How to use keyTextTransform() for nested json?
body: <p>My model has a json field. I can access jsonfield['key1'] with the following query</p>
  <pre><code>from django.contrib.postgres.fields.jsonb import KeyTextTransform
  MyModel.objects.annotate(val=KeyTextTransform('key1', 'jsonfield')).order_by('val')
  </code></pre>
  <p>But how can I access a key like jsonfield['key1']['key2'] or even more nested ones?</p>
  <p>This can't be the only solution, right?</p>
  <pre><code>MyModel.objects.annotate(val=KeyTextTransform('key2', (KeyTextTransform('key1', 'jsonfield'))).order_by('val')
  </code></pre>