Fatal error: Uncaught Error: Interface "Symfony\Component\Serializer\Mapping\ClassDiscriminatorResolverInterface" not found in /srv/disk3/2724534/www/transdoetaskforce.org/concrete/vendor/symfony/serializer/Mapping/ClassDiscriminatorFromClassMetadata.php:19 Stack trace: #0 {main} thrown in /srv/disk3/2724534/www/transdoetaskforce.org/concrete/vendor/symfony/serializer/Mapping/ClassDiscriminatorFromClassMetadata.php on line 19