login stays on page

As a student, when I scan a QR Code to redeem a stamp, I want this to work even when I'm not logged in yet.

Flow: Scan QR Code --> /redeem?token=x --> login through oauth --> /redeem?token=x --> /users/x/redeem?token=x

As a users of Stempelheft, when I am viewing one of the public pages, and click on login, I want to get back to the same page after the login