Ajax callback for the dragdrop mode.
array $form: An associate array containing the structure of the form.
\Drupal\Core\Form\FormStateInterface $form_state: The current state of the form.
array The container form element.
public static function dragDropModeAjax(array $form, FormStateInterface $form_state) {
$submit = ParagraphsWidget::getSubmitElementInfo($form, $form_state, ParagraphsWidget::ACTION_POSITION_HEADER);
$submit['element']['#prefix'] = '<div class="ajax-new-content">' . (isset($submit['element']['#prefix']) ? $submit['element']['#prefix'] : '');
$submit['element']['#suffix'] = (isset($submit['element']['#suffix']) ? $submit['element']['#suffix'] : '') . '</div>';
return $submit['element'];
}