public function unlink($resource, $id, $relation, $related, $relatedId)
 {
     $model = new $resource();
     $repository = new EloquentRepository($model);
     $entity = $repository->find($id);
     $related = new $related();
     $repository->setModel($related);
     $related = $repository->find($relatedId);
     return $repository->detach($entity, $relation, $related);
 }