title: React-admin CheckboxGroupInput check some checkboxes by default
body: <p>how to make some checkboxes checked by default</p>
  <pre><code>    &lt;CheckboxGroupInput
        source=&quot;my_junction_table&quot;
        choices={choices}
        optionText={&lt;KioskCheckbox /&gt;}
        initialValue={[{ id: 4, checked: true }]}  // don't work
        defaultValue={[{ id: 4, checked: true }]}  // don't work
        options={{ checked: true }}                // check all
        optionValue=&quot;id&quot;
      /&gt;
  </code></pre>
  <p>with</p>
  <pre><code>options={{ checked: true }}
  </code></pre>
  <p>all the checkboxes are checked</p>
  <p>with</p>
  <pre><code>initialValue={[{ id: 4, checked: true, value: true }]}
  defaultValue={[{ id: 4, checked: true }]}
  </code></pre>
  <p>nothing work, I've already see the doc and the code in react-admin repo, can't find anything about that.</p>