refactor: changed "Article does not exist" status code to 404

server/apps/research/views.py

@@ -90,7 +90,7 @@ def retrieve_by_identifier(self, request, identifier=None):
         except Exception as e:
             logger.error(f"Error retrieving article by identifier: {e}")
             return Response({'error': 'Article does not exist'}, 
-                          status=status.HTTP_500_INTERNAL_SERVER_ERROR)
+                          status=status.HTTP_404_NOT_FOUND)
 
     # Custom action to retrieve articles by category
     @action(detail=False, methods=['get'], url_path=r'category/(?P<category>[-\w]+)')