code: private BackchannelAuthenticationCompleteResponse fail(
              String ticket, String subject, Result result, String errorDescription,
              URI errorUri)
      {
          return callBackchannelAuthenticationComplete(
                  ticket, subject, result, 0, null, null, null, null, errorDescription,
                  errorUri);
      }
docs: Call Authlete's {@code /api/backchannel/authentication/complete} API with an unsuccessful
  result.
  
  @param ticket
  A ticket that was issued by Authlete's {@code /api/backchannel/authentication}
  API.
  
  @param subject
  The subject of the authenticated user.
  
  @param result
  The result of end-user authentication and authorization.
  
  @param errorDescription
  The description of the error.
  
  @param errorUri
  The URI of a document which describes the error in detail.
  
  @return
  A response from Authlete's {@code /api/backchannel/authentication/complete}
  API.