code: protected function isValidCallback(Request $httpRequest)
      {
          return $this->session->has("provider")
              && $httpRequest->query->has("state")
              && $this->session->has("oauth2state")
              && is_string($this->session->get("oauth2state"))
              && (strlen($this->session->get("oauth2state")) > 0);
      }
docs: Checks if the request and session have all the required fields for a OAuth 2.0 callback
  
  - The session must have "provider" name which is the provider the callback
  would be returned from.
  - The request must have "state" query param as a CSRF prevention.
  - The session must have "oauth2state" which must be a string
  a must be non-empty.
  
  @param Request $httpRequest
  @return bool true if the required fields are present, false otherwise