feat(udp,http3): add UDP datagram handler relay support and stream HTTP/3 request bodies to backends

rust/crates/rustproxy/src/lib.rs

@@ -1008,7 +1008,7 @@ impl RustProxy {
     /// Set the Unix domain socket path for relaying UDP datagrams to TypeScript datagramHandler callbacks.
     pub async fn set_datagram_handler_relay_path(&mut self, path: Option<String>) {
         info!("Datagram handler relay path set to: {:?}", path);
-        if let Some(ref udp_mgr) = self.udp_listener_manager {
+        if let Some(ref mut udp_mgr) = self.udp_listener_manager {
             if let Some(ref p) = path {
                 udp_mgr.set_datagram_handler_relay(p.clone()).await;
             }