docs: public byte[] downloadAttachmentContent(Attachment issueAttachment)
              throws RedmineException {
          final ByteArrayOutputStream baos = new ByteArrayOutputStream();
          downloadAttachmentContent(issueAttachment, baos);
          try {
              baos.close();
          } catch (IOException e) {
              throw new RedmineInternalError();
          }
          return baos.toByteArray();
      }