[keycloak-dev] Thinking about step-up authentication and token timeouts

Clients should be able to obtain tokens with reduced scope and longer or shorter expiration, then later request new tokens with increased scope and different expiration. They should also be able to require different levels of authentication and also require re-authentication. An application may for example: * At first only need users email - this would allow showing the name + email. In this situation a long expiration access token in combination with implicit flow would do. It's also not necessary to re-authenticate the user and a user that has been logged-in for months or even a year is fine. * When a user clicks on orders it would require the password and extend scope to be able to view orders. Now you'll want to switch to short expiration access tokens and authorization code grant. You'll also want to make sure the user logged-in fairly recently, max 30 days could be sensible. * When a user tries to purchase something the user now has to provide the OTP to be able to purchase with saved credit card details. You'll also want to make sure the user logged-in very recently, max a day could be required. There may also be cases where you always want the user to re-authenticate, for example when trying to purchase something over a certain price level.