title: Select keys with boolean value true in PostgreSQL json query
body: <p>In my <strong>PostgreSQL</strong> <strong>11.6</strong> table I have a <strong>json</strong> field <code>app_settings</code> with data on the following format:</p>
  
  <pre><code>{
     "my_app": {
        "features": {
           "very_good_feature": true,
           "awesome_feature": false,
           "even_better_feature": true
        }
     }
  }
  </code></pre>
  
  <p>I want to create a query that selects a list of feature names where the feature has the value <code>true</code>. So in the example above, I would like the result of the query simply to be 2 rows like this:</p>
  
  <ol>
  <li>very_good_feature</li>
  <li>even_better_feature</li>
  </ol>
  
  <p>I can successfully select ALL the keys with the following query:</p>
  
  <pre><code>select
      json_object_keys(app_settings -&gt;'my_app' -&gt; 'features') as k
  from
      my_table;
  </code></pre>
  
  <p><em>How can I write the <code>where</code> clause to only list the ones with <code>true</code> as value?</em></p>