Log a user in via OAuth2 in a popup window, without requiring a redirect

Sample usage:

{{#oauth-popup
  authUrl=authUrl
  loginSuccess=(action 'loginSuccess')
  loginFail=(action 'loginFail') as |popup|}}
   <button class="btn btn-default login-button" onclick={{action 'login' target=popup}} >
      Login to OSF
   </button>
{{/oauth-popup}}