Add::checkStage

public function checkStage(): Result
{
	$result = new Result();

	$firstStage = $this->item->getType()->getFirstStage();
	if(!$firstStage)
	{
		$result->addError($this->getEmptyStageError());
	}
	elseif($this->item->getStageId() !== $firstStage->getId())
	{
		$result->addError($this->getWrongStageError($firstStage->getName()));
	}

	return $result;
}