CustomFieldsController::initialize

public function initialize(Entity $entity) : Entity
{
	if ($entity->getId() <= 0)
	{
		return $entity;
	}

	$dbRes = CustomFieldsTable::getList([
		'select' => ['ID', 'FIELD'],
		'filter' => [
			'=ENTITY_ID' => $entity->getId(),
			'=ENTITY_TYPE' => $entity::getRegistryEntity(),
			'=ENTITY_REGISTRY_TYPE' => $entity::getRegistryType()
		]
	]);

	while ($data = $dbRes->fetch())
	{
		$entity->markFieldCustom($data['FIELD']);
	}

	return $entity;
}