The logic of deleting price_list_item in pricelist's postdelete is wrong

1. The logic of deleting price_list_item in pricelist's postdelete is wrong

   class PriceListItemStorage extends CommerceContentEntityStorage implements PriceListItemStorageInterface {
     public function loadMultipleByPriceList($price_list_id) {
       $entity_query = $this->getQuery();
       $entity_query->condition('price_list_id', $price_list_id);
       $entity_query->sort('weight');
       $result = $entity_query->execute();
       return $result ? $this->loadMultiple($result) : [];
     }
   }
   class PriceList extends CommerceContentEntityBase implements PriceListInterface {
     public function getItems() {
       // TODO: Implement getItems() method.
       $storage = $this->entityTypeManager()->getStorage('price_list_item');
       return $storage->loadMultipleByPriceList($this->id());
     }
     public static function postDelete(EntityStorageInterface $storage, array $entities) {
       // Delete the price list item of a deleted price list.
       foreach ($entities as $entity) {
         $price_list_items = $entity->getItems();
         if (empty($price_list_items)) {
           continue;
         }
   
         $price_list_item_storage = \Drupal::service('entity_type.manager')
           ->getStorage('price_list_item');
         $price_list_item_storage->delete($price_list_items);
       }
     }
   }
   

   The logic of getting the needed deleted price_list_item in loadMultipleByPriceList() is wrong,
   The right way of getting one price_list's price_list_items is directly from EntityReference, not writing complicated filtering logic like

       $entity_query = $this->getQuery();
       $entity_query->condition('price_list_id', $price_list_id);
       $entity_query->sort('weight');
       $result = $entity_query->execute();
   

   .

2. The value of price_list_item's price_list_id field should be generated in entity level through postSave(), not form level. because "form level" will cause price_list_id be NULL when the price_list_item was added to price_list by api of code

   $pricelist->get('field_price_list_item')->appendItem($priceListItem);
   

The above two problem caused one bug: When delete a pricelist, it's price_list_item can't be deleted when price_list_id is NULL.