app = FastAPI(generate_unique_id_function=custom_generate_unique_id)
    router = APIRouter()

    @app.post("/", response_model=List[Item], responses={404: {"model": List[Message]}})
    def post_root(item1: Item, item2: Item):
        return item1, item2  # pragma: nocover

    @router.post(
        "/router", response_model=List[Item], responses={404: {"model": List[Message]}}
    )