code: protected function validateTokenParams()
      {
          if (empty($this->tokenUrl) || filter_var($this->tokenUrl, FILTER_VALIDATE_URL) === false) {
              throw new Oauth2ClientException(sprintf(self::INVALID_TOKEN_URL, $this->tokenUrl));
          }
  
          if (empty($this->clientId)) {
              throw new Oauth2ClientException(self::INVALID_CLIENT_ID);
          }
  
          if (empty($this->clientSecret)) {
              throw new Oauth2ClientException(self::INVALID_CLIENT_SECRET);
          }
  
          return true;
      }
docs: Validates params for the token request
  @author Adegoke Obasa <goke@cottacush.com>
  @return bool
  @throws Oauth2ClientException