message: `rust-server-codegen`: don't check JSON Content-Type header if there is no body
diff: @@ -138,7 +138,6 @@ private class ServerHttpProtocolImplGenerator(
  } else {
  """
  async fn from_request(req: &mut #{Axum}::extract::RequestParts<B>) -> Result<Self, Self::Rejection> {
  - #{SmithyHttpServer}::protocols::check_json_content_type(req)?;
  Ok($inputName(#{parse_request}(req).await?))
  }
  """.trimIndent()
  @@ -481,7 +480,10 @@ private class ServerHttpProtocolImplGenerator(
  """
  let body = request.take_body().ok_or(#{SmithyHttpServer}::rejection::BodyAlreadyExtracted)?;
  let bytes = #{Hyper}::body::to_bytes(body).await?;
  + if !bytes.is_empty() {
  + #{SmithyHttpServer}::protocols::check_json_content_type(request)?;
  input = #{parser}(bytes.as_ref(), input)?;
  + }
  """,
  *codegenScope,
  "parser" to parser,
  