docs: protected String getRemoteAddr(ApiRequest request, IPListConfig config) {
          String httpHeader = config.getHttpHeader();
          if (httpHeader != null && httpHeader.trim().length() > 0) {
              String value = (String) request.getHeaders().get(httpHeader);
              if (value != null) {
                  return value;
              }
          }
          return request.getRemoteAddr();
      }