// main IDP configuration URLs
    protected $openidconnect = true;  // Google supports OpenID-Connect
    protected $authTokenUrl  = 'https://accounts.google.com/o/oauth2/auth';
    protected $accessTokenUrl= 'https://www.googleapis.com/oauth2/v3/token';
    // I fail to get Google People OpenIdConnect API to work :(
    //protected $identityApiUrl= 'https://www.googleapis.com/plus/v1/people/me/OpenIdConnect';
    protected $identityApiUrl= 'https://www.googleapis.com/oauth2/v1/userinfo';

    // OAuth2 action-1:  getAuthUrl($state) build authorization token url
    protected $scopes = ['openid','email','profile'];  // request authentication & email

[apache@vz-bzh GeoToBe]$ curl -X GET -H "Authorization: Bearer ya29.5ABSl_75eP_zYFho_E-wVjPlZJc1XfY398HZqJjMxvRxBEWteLKZwNeh2v0BPwWuoH1iLpESeBQvFw" https://www.googleapis.com/plus/v1/people/me/openIdConnect
{
 "error": {
  "errors": [
   {
    "domain": "usageLimits",
    "reason": "accessNotConfigured",
    "message": "Access Not Configured. The API is not enabled for your project, or there is a per-IP or per-Referer restriction configured on your API key and the request does not match these restrictions. Please use the Google Developers Console to update your configuration.",
    "extendedHelp": "https://console.developers.google.com"
   }
  ],
  "code": 403,
  "message": "Access Not Configured. The API is not enabled for your project, or there is a per-IP or per-Referer restriction configured on your API key and the request does not match these restrictions. Please use the Google Developers Console to update your configuration."
 }
}