fix api spec

backend/src/routes/documents.rs

@@ -186,7 +186,11 @@ pub async fn get_document(
     responses(
         (status = 201, description = "Document created", body = DocumentDetailResponse),
         (status = 200, description = "Existing document reused", body = DocumentDetailResponse),
-        (status = 409, description = "Document with identical contents already exists")
+        (
+            status = 409,
+            description = "Document with identical contents already exists",
+            body = crate::error::ApiErrorResponse
+        )
     ),
     tag = "Documents"
 )]