"/post-callback",
        response_model=list[Item],
        responses={404: {"model": list[Message]}},
        generate_unique_id_function=custom_generate_unique_id3,
    )
    def post_callback(item1: Item, item2: Item):
        return item1, item2  # pragma: nocover

    @app.post(
        "/",
        response_model=list[Item],
        responses={404: {"model": list[Message]}},