Function tunnel_via_proxy 

pub async fn tunnel_via_proxy(
    target: &WsTarget,
    proxy: &ProxyTarget,
) -> Result<ProxiedStream, TransportError>

Establish a tunneled connection through proxy to the WebSocket target.

On success the returned stream is positioned right after the proxy’s 200/2xx response, ready for the WebSocket handshake. The function does not perform the WebSocket handshake itself; callers wrap the stream in tokio-tungstenite::client_async.

Errors

Returns a TransportError when:

• The TCP connection to the proxy fails (TransportError::Io).
• The TLS layer to the proxy or upstream cannot be established (TransportError::Tls).
• The proxy returns a non-success status, malformed headers, or closes the stream before completing the response (TransportError::Handshake).