/**
* Adds new document to database, returns id if success, error otherwise
* @param $document_input
* @return mixed
*/
public function add($document_input)
{
$document_id = parent::add($document_input);
return $this->addContentToDocument($document_input->getTargetGroups(), $document_input->getLinks(), $document_input->getFields(), $document_id);
}
