Google OAuth:未配置访问权限

我正在尝试为我的应用程序设置Google Oauth身份验证。我已经创建了GoogleAPI项目并设置了重定向URI。当我使用link进行身份验证时，我会得到一个响应：

{"errors"=>[{"domain"=>"usageLimits", "reason"=>"accessNotConfigured", "message"=>"Access Not Configured. Please use Google Developers Console to activate the API for your project."}], "code"=>403, "message"=>"Access Not Configured. Please use Google Developers Console to activate the API for your project."}: 
{
 "error": {
  "errors": [
   {
    "domain": "usageLimits",
    "reason": "accessNotConfigured",
    "message": "Access Not Configured. Please use Google Developers Console to activate the API for your project."
   }
  ],
  "code": 403,
  "message": "Access Not Configured. Please use Google Developers Console to activate the API for your project."
 }
}

据我所知，我应该从我的谷歌开发者控制台激活一些API。问题是我不清楚我应该从87项列表中激活什么api：

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据我所知，站点身份验证所需的API是Google+

您到底想做什么？为什么要启用Google oauth？您为我省去了很多麻烦！谢谢