message: #resolve do not assert trailer
  do not assert parser.complete() in ServerRequest::requestDone()
  because it is possible that the TrailerParser is not error but
  not complete if there is nothing to read from the stream
diff: @@ -864,8 +864,16 @@ ServerRequest::requestDone()
  cancel();
  throw std::runtime_error("Error parsing trailer");
  }
  - MORDOR_ASSERT(parser.complete());
  + // it is possible that the TrailerParser is not error but not complete
  + // if there is nothing to read from the stream
  + // according to https://tools.ietf.org/html/rfc7230#section-4.1.2
  + // chunked trailer is optional
  + if (parser.complete()) {
  MORDOR_LOG_DEBUG(g_log) << m_context << " " << m_requestTrailer;
  + } else if (!m_request.general.trailer.empty()) {
  + MORDOR_LOG_WARNING(g_log) << m_context
  + << " request has non empty trailer header but no trailer part";
  + }
  }
  m_conn->requestComplete(this);
  }
  