update openapi docs for PUT request

main.py

@@ -44,7 +44,11 @@ async def list_items(db: Session = Depends(get_db)):
     return {i.id: i for i in items}
 
 
-@app.put("/api/items/{id}")
+@app.put(
+    "/api/items/{id}",
+    status_code=201,
+    responses={201: {"description": "created"}, 204: {"description": "updated"}},
+)
 async def put_item(id: str, item: Item, db: Session = Depends(get_db)):
     if item.last_updated is None:
         item.last_updated = month_timestamp()