@Override
        public void onComplete() {
            CompletableFutures.allAsList(bodyPartFutures)
                              .handle((parts, cause) -> {
                                  if (cause != null) {
                                      completionFuture.completeExceptionally(cause);
                                  } else {
                                      completionFuture.complete(parts);
                                  }
                                  return null;
                              });
        }
Returns a random boundary used for encoding multipart messages.
core/src/main/java/com/linecorp/armeria/common/multipart/DefaultMultipart.java