Update sourceEntity when copying parent association mappings

When ORMMappedSuperClassSubscriber copies association mappings from
a parent mapped-superclass to a child entity, it must update the
sourceEntity to point to the concrete child class. Without this,
Doctrine's BasicEntityPersister generates incorrect SQL table aliases
for eager-loaded inverse one-to-one associations, because the alias
cache key uses the mapped-superclass name instead of the concrete
entity name.

This mirrors what Doctrine's own ClassMetadataFactory::addInheritedRelations()
does when processing inheritance.

Author: mpysiak

src/Bundle/EventListener/ORMMappedSuperClassSubscriber.php

@@ -87,6 +87,13 @@ private function setAssociationMappings(ClassMetadata $metadata, Configuration $
                 foreach ($parentMetadata->getAssociationMappings() as $key => $value) {
                     $type = \is_array($value) ? $value['type'] : $value->type();
                     if ($this->isRelation($type) && !isset($metadata->associationMappings[$key])) {
+                        if (\is_array($value)) {
+                            $value['sourceEntity'] = $class;
+                        } else {
+                            /** @psalm-suppress UndefinedClass */
+                            $value->sourceEntity = $class; /** @phpstan-ignore-line */
+                        }
+
                         $metadata->associationMappings[$key] = $value; /** @phpstan-ignore-line */
                     }
                 }