std::visit([](auto& v){ decltype(v)::value_type r; f.setup_body(h, r); }, f.body_for(h)) (setup_body must be a visitor over the value_types of the response bodies returned by f.body_for(h))
http_callback
Callback type used to provide responses to http(s) requests. Takes another type that satisfies response_filter, referred to as Filter from now on.
Requires:
std::move_constructible
(malloy::http::response<Ts>&&) -> void where Filter::body_for(..) -> std::variant<Ts...>.