fix: relation filtering for Strapi v5 Document Service API

This commit fixes a critical bug where link mappings were not found
due to incorrect relation filter syntax in Strapi v5.

Changes:
- Use { relation: { documentId: value } } for relation filters
- Fix userId filters to use documentId (string) instead of parseInt
- Use count() instead of findMany().length for performance

Fixes: Link mapping not found errors (e.g., b7d1775f8a9e38000d53a04af63ed1f0/8ea5bd41)

Author: Schero94

.releaserc.json

@@ -15,4 +15,3 @@
     ]
   ]
 }
-