title: redirect_uri_mismatch when OAuth2 account linking from Google Home Simulator
body: <p>I am developing an account linking integration for an "Actions on Google" integration with API.AI for use with Google Home. When I test this agent in the simulator (<a href="https://developers.google.com/actions/tools/web-simulator" rel="nofollow noreferrer">https://developers.google.com/actions/tools/web-simulator</a>)</p>
  
  <p>As expected, this is my response:</p>
  
  <pre><code>{
      "response": "It looks like your conference manager account is not linked yet. You can link conference manager to your Google Account from the Google Home app.",
      "audioResponse": "//NExAARC..."content_copy,
      "debugInfo": {
          "sharedDebugInfo": [
              {
                  "name": "Account Linking Url",
                  "debugInfo": "https://assistant.google.com/services/auth/handoffs/auth/start?provider={project-id}_dev&amp;return_url=https://www.google.com/"
              }
          ]
      }
  }
  </code></pre>
  
  <p>However, when I follow the </p>
  
  <pre><code>res.debugInfo.sharedDebugInfo[0].debugInfo
  </code></pre>
  
  <p>link, I get the standard <strong><em>redirect_uri_mismatch</em></strong> error page, with the details:</p>
  
  <blockquote>
    <p>The redirect URI in the request,
    <a href="https://oauth-redirect.googleusercontent.com/r/" rel="nofollow noreferrer">https://oauth-redirect.googleusercontent.com/r/</a><strong><em>my-project-id</em></strong>,
    does not match the ones authorized for the OAuth client. Visit
    <a href="https://console.developers.google.com/apis/credentials/oauthclient/" rel="nofollow noreferrer">https://console.developers.google.com/apis/credentials/oauthclient/</a><strong>my-client-id</strong>?project=<strong>my-client-id</strong>
    to update the authorized redirect URIs.</p>
    
    <p>It's of course not possible to add the <strong>googleusercontent</strong> domain to
    the redirects, and this isn't the redirect I have specified in my
    API.AI Actions on Google intergration.</p>
  </blockquote>
  
  <p>On the API.AI side my Auth Url is the standard Google one:
  <code>https://accounts.google.com/o/oauth2/v2/auth</code></p>
  
  <p>and my token URL is:
  <code>https://myendpoint.com/google-home-token-endpoint</code>
  with the Scopes filled in as <code>calendar</code></p>
  
  <p>On the google developer console, I have the token URL set to the same as in API.AI, and the project id/client id the same as reference in the requests.</p>
  
  <p>Is this a known issue? Additional debugging efforts I can try?</p>