Function moq_origin_dynamic_cancel 

#[unsafe(no_mangle)]
pub extern "C" fn moq_origin_dynamic_cancel(dynamic: u32) -> i32

Stop serving and retract the route.

Returns immediately: zero on success, or a negative code if already closed. The moq_origin_dynamic on_request callback still fires once more with a terminal 0 (or a negative error), and that final callback is where user_data should be released.