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;
    }