Duplicated Tag unique constraint error when creating multiple Content with same Tag

[alexander-schranz]

When we are creating a Document 1 with a Tag A and create a Document 2 also with a Tag A and the Tag A did not exist the TagFactory currently will create for Document 1 and Document 2 a new Tag aslong as between no "flush" of the entityManager was called and will error in a UniqueConstraint.

This can be fixed by #175 or a low version of it by just cache newly created tags and check for newly tags in the TagFactory:

        foreach ($tagNames as $key => $tagName) {
            if (isset($excerptTags[$key])) {
                continue;
            }
            
+            $tag = $this->createdTags[$tag->getName()] ?? null;

+            if (!$tag) {
                /** @var TagInterface $tag */
                $tag = $this->tagRepository->createNew();
                $tag->setName($tagName);
   
                $this->entityManager->persist($tag);
+               $this->createdTags[$tag->getName()] = $tag;
+            }

            $excerptTags[$key] = $tag;
        }