code: private function configureVatNumberSubjectMapping(LoadClassMetadataEventArgs $eventArgs)
      {
          /** @var ClassMetadata $metadata */
          $metadata = $eventArgs->getClassMetadata();
          $class = $metadata->getName();
  
          // Check class
          if (!is_subclass_of($class, Pricing\Model\VatNumberSubjectInterface::class)) {
              return;
          }
  
          // Don't add twice
          if (in_array($class, $this->vatNumberSubjectClassCache)) {
              return;
          }
  
          // Add mappings
          $this->addMappings($metadata, $this->getVatNumberSubjectMappings());
  
          // Cache class
          $this->vatNumberSubjectClassCache[] = $class;
      }
docs: Configures the vat number subject mapping.
  
  @param LoadClassMetadataEventArgs $eventArgs