title: Using ReferenceArrayInput with a none-flat array
body: <p>I have a record that looks like so:</p>
  
  <pre><code>Item {
     itemId: 1,
     categories: [{id: 123, categoryId: 657, itemId: 1}, ...]
  }
  </code></pre>
  
  <p>(The item is pulled from rest service based on nestjsx/crud, mostly automatic, and i really want to avoid any changes there.)</p>
  
  <p>ReferenceArrayInput is expecting a flat array, with direct reference to the ids. {categories: [657, ...]}</p>
  
  <p>I'm looking for a way to tell him to look at a nested object property.
  Or a hook, that will let me transform the records to the appropriate format.</p>
  
  <p>For the visual part, i intend to use AutocompleteArrayInput</p>