Problem:
My organisation, ExampleFooBar, uses Google Apps. On our website I want to enable OpenID Single Sign-In (like StackOverflow), but only allow @examplefoobar.com email addresses to sign in. What OpenID url should I use for a Google Apps email address?
As per comments on Include OpenId in drupal, the domain
http://www.google.com/profiles/<username>
can be used for normal Google accounts, but this doesn't work for Google Apps accounts.Google also provides the url
https://www.google.com/accounts/o8/id
but using that would allow any google user who found our website's login page to sign in, as the sign-in page accepts any google account name.
What Google URL can I use to ensure only @examplefoobar.com email addresses can sign in?
Google documentation for Google Apps OpenID is at http://code.google.com/googleapps/domain/sso/openid_reference_implementation.html, but is incredibly unhelpful.