code: private function configureSubjectRelativeMapping(LoadClassMetadataEventArgs $eventArgs)
      {
          /** @var ClassMetadata $metadata */
          $metadata = $eventArgs->getClassMetadata();
          $class = $metadata->getName();
  
          // Check class
          if (!is_subclass_of($class, SubjectRelativeInterface::class)) {
              return;
          }
  
          // Don't add twice
          if (in_array($class, $this->relativeClassCache)) {
              return;
          }
  
          // Map embedded
          $this
              ->getSubjectIdentityMapper($eventArgs->getEntityManager())
              ->processClassMetadata($metadata, 'subjectIdentity', 'subject_');
  
          // Cache class
          $this->relativeClassCache[] = $class;
      }
docs: Configures the subject relative mapping.
  
  @param LoadClassMetadataEventArgs $eventArgs