Function handle_request 

async fn handle_request<T>(
    writer: Arc<Mutex<WriteHalf<Box<dyn PtStream>>>>,
    addr: Url,
    rh: Arc<impl RequestHandler<T> + 'static>,
    ex: Arc<Executor<'_>>,
    tasks: Arc<Mutex<HashSet<Arc<StoppableTask>>>>,
    settings: RpcSettings,
    req: JsonRequest,
) -> Result<()>

Auxiliary function to handle a request in the background.