title: force google to refresh token via python social auth
body: <p>We're working on a project that depends on PSA (0.2.1) for authentications with google oauth2 (offline). Somehow we lost some refresh tokens of some users, we want to force those users to RE-AUTHENTICATE so we can get new refresh token from google</p>
  
  <p>we tried both :</p>
  
  <ol>
  <li>Diconnect those users using /diconnect/google-oauth2, we got a NotAllowedToDisconnect exception, even after removing <code>social.pipeline.disconnect.allowed_to_disconnect</code> from <code>SOCIAL_AUTH_DISCONNECT_PIPELINE</code>, we got no exception, but when the user re-authenticate, there is no refreh_token in google response</li>
  <li>add approval_prompt=force to 'account:social:begin' url, but it doesn't return the refresh_token</li>
  </ol>
  
  <p>Any idea will be highly appreciated.</p>
  
  <p><em>Update</em>: We tried to use <code>{% url 'account:social:begin' 'google-oauth2' %}?approval_prompt=force&amp;next=/</code> to force the approval_prompt for certain users (with missing tokens), but its seem to have no effect over google oauth.</p>
  
  <p>Thanks</p>