title: How to set different entry_options for each CollectionType entry in Symfony FormBuilder
body: <p>I'm trying to create multiple <code>HiddenType</code> fields in with Form Builder using <code>CollectionType</code>, to group these fields when I'm dealing with them in my controller. But I want each field to have different attributes. Is it possible to use <code>entry_options</code> to set different options for each entry?</p>
  
  <p>I'm using a javascript drag and drop plugin to drop elements in a container, when these elements are dropped a JS code updates these hidden fields that, I use to capture the information in my controller. So is mandatory that these fields are grouped somehow so I can deal with them easily in my controller.</p>
  
  <p>An example:</p>
  
  <pre><code>$builder-&gt;add(self::FIELD_MAPPED_COLUMNS, CollectionType::class, [
      'entry_type'    =&gt; HiddenType::class,
      'data'          =&gt; ['field1', 'field2', 'field3'],
      'label'         =&gt; false,
      'entry_options' =&gt; [
          'attr' =&gt; [
              'data-my-field' =&gt; '?????'
          ]
      ]
  ])-&gt;add('submit', SubmitType::class);
  </code></pre>
  
  <p>I want to set a different <code>data-my-field</code> for each <code>HiddenType</code> so I can use it in Javascript. Is it possible?</p>