Function forward_subscription 

pub async fn forward_subscription(
    socket: WebSocket,
    subscription: EventSubscription,
    gate: NamespaceEventGate,
    outbound_buffer_bound: usize,
) -> Result<(), ServerError>

Forward a previously authorized engine subscription to a WebSocket.

The reader task is aborted on every exit path — success, terminal error frame, and frame-encoding failure alike — so it can never linger holding a broadcast receiver after the socket loop ends.

Errors

Returns ServerError when the stream ends with a terminal error frame (lag, gate failure, encoding failure) or a wire frame cannot be encoded.