@Override
                    protected void onRequest(long n) {
                        // A BodyPart is converted to a StreamMessage<HttpData> one to one.
                        upstream.request(n);
                    }
Reactive processor that encodes a stream of {@link BodyPart}s into an HTTP payload.
core/src/main/java/com/linecorp/armeria/common/multipart/MultipartEncoder.java