code: private void abortMultipartUpload(WebContext ctx, String uploadId) {
          multipartUploads.remove(uploadId);
          ctx.respondWith().status(HttpResponseStatus.OK);
          delete(getUploadDir(uploadId));
      }
docs: Handles DELETE /bucket/id?uploadId=X
  
  @param ctx      the context describing the current request
  @param uploadId the multipart upload that should be cancelled