title: Using final-form-array in a nested object
body: <p>I have a scenario where I have multiple grids and in each grid can have multiple rows that can be deleted.</p>
  <pre><code>{ 
  document: [{
  rows: [{
  make: &quot;Tesla&quot;
  }]
  }
  </code></pre>
  <p>I wanted to do something like <code>&lt;FieldArray name=&quot;document[0]&quot;&gt;</code> that way, I can give the grid add and remove functionality but it seems the fieldarray only takes single nodes. Is there a work around for this or am i doing something wrong?</p>
  <p>Initially I had <code>document1: { [{...fields}] }</code> so useField looked like this:</p>
  <pre><code>useField(`${fieldKey}${fieldIndex}[${rowIndex}].${field}`)
  </code></pre>
  <p>but I wanted to use yup schema validations due to issues with ag-grid and validations at the cell level so I figured it'd be easier if I used generic keys.</p>
  <pre><code>fields.removeBatch(gridApi.getSelectedNodes().map(({ rowIndex }) =&gt; rowIndex));
  </code></pre>