code: public static Conflict of(int errorCode, Throwable cause) {
          if (_localizedErrorMsg()) {
              return of(errorCode, cause, defaultMessage(CONFLICT));
          } else {
              touchPayload().errorCode(errorCode).cause(cause);
              return _INSTANCE;
          }
      }
docs: Returns a static Conflict instance and set the {@link #payload} thread local
  with error code and cause specified
  
  When calling the instance on {@link #getMessage()} method, it will return whatever
  stored in the {@link #payload} thread local
  
  @param cause  the cause
  @param errorCode the app defined error code
  @return a static Conflict instance as described above