message: docs(examples): add a length check to reversed echo route
diff: use std::net::SocketAddr;
  +use hyper::body::HttpBody as _;
  use hyper::server::conn::Http;
  use hyper::service::service_fn;
  use hyper::{Body, Method, Request, Response, StatusCode};
  @@ -38,6 +39,15 @@ async fn echo(req: Request<Body>) -> Result<Response<Body>, hyper::Error> {
  // So here we do `.await` on the future, waiting on concatenating the full body,
  // then afterwards the content can be reversed. Only then can we return a `Response`.
  (&Method::POST, "/echo/reversed") => {
  + // To protect our server, reject requests with bodies larger than
  + // 64kbs of data.
  + let max = req.body().size_hint().upper().unwrap_or(u64::MAX);
  + if max > 1024 * 64 {
  + let mut resp = Response::new(Body::from("Body too big"));
  + *resp.status_mut() = hyper::StatusCode::PAYLOAD_TOO_LARGE;
  + return Ok(resp);
  + }
  +
  let whole_body = hyper::body::to_bytes(req.into_body()).await?;
  let reversed_body = whole_body.iter().rev().cloned().collect::<Vec<u8>>();
  