docs: public Map<String, String> getPrintableHeaders() {
      final Map<String, String> headers = new HashMap<String, String>(
          request.headers().entries().size());
      for (final Entry<String, String> header : request.headers().entries()) {
        if (header.getKey().toLowerCase().equals("cookie")) {
          // null out the cookies
          headers.put(header.getKey(), "*******");
        } else {
          // http://tools.ietf.org/html/rfc2616#section-4.2
          if (headers.containsKey(header.getKey())) {
            headers.put(header.getKey(), 
                headers.get(header.getKey()) + "," + header.getValue());
          } else {
            headers.put(header.getKey(), header.getValue());
          }
        }
      }
      return headers;
    }