protected function getTokenByClientCredentialsGrant()
    {
        $token = $this->getAuthorizationServer()->getAccessToken('client_credentials', [
            'scope' => $this->config['client_credentials']['scope'],
        ]);

        $this->getFrameworkBridge()->persistClientToken(
            $this->config['client_credentials']['client_id'],
            $token->getToken(),
            $token->getExpires(),
            $token->getValues()['role']
        );

        return $token;
    }