CCalendar::getUserLanguageId

static function getUserLanguageId(?int $userId): string
{
	if (!$userId)
	{
		return LANGUAGE_ID;
	}

	if (isset(self::$userLanguageId[$userId]))
	{
		return self::$userLanguageId[$userId];
	}

	$user = MainUserTable::query()
		->where('ID', $userId)
		->setSelect(['NOTIFICATION_LANGUAGE_ID'])
		->exec()
		->fetch()
	;

	self::$userLanguageId[$userId] = $user['NOTIFICATION_LANGUAGE_ID'] ?? LANGUAGE_ID;

	return self::$userLanguageId[$userId];
}