community_store: Can't refresh doctrine entities, got discriminator map error

Some guys already reported in the past, but I got the same error, so raised the new issue.

Exception Occurred: /path/to/concrete/vendor/doctrine/orm/lib/Doctrine/ORM/Mapping/MappingException.php:679 Entity 'Concrete\Package\CommunityStore\Entity\Attribute\Key\StoreProductKey' has to be part of the discriminator map of 'Concrete\Core\Entity\Attribute\Key\Key' to be properly mapped in the inheritance hierarchy. Alternatively you can make 'Concrete\Package\CommunityStore\Entity\Attribute\Key\StoreProductKey' an abstract class to avoid this exception from occurring. (0)

Related issues: #422 #439