redirecting from hook_user_login()

In Drupal 7 from the hook_user_login() you were able to change the $edit['redirect'] and cause the user to be redirected after login to the user would get redirected to the page, However this ability was lost during the Drupal 8 rewrite.

I was using the redirect after login which leveraged hook_user_login() and just printed the RedirectResponse() to redirect the user. I had to do some changes to that module to make it work with an ajax login, and added an exit() so we would not cause any problems.

My client is also using the Janrain module for SSO, and if I just exit() hook_janrain_capture_user_authenticated() doesn't get called when users login.

I am going to try removing the exit() from hook_user_login() and see how this acts, but I am not 100% sure =what side effects will this have.

What I asking is, is there a better method to do this, a Drupal 8 way or will there need to be some changes like changing hook_user_login() to return an Url() object and this is what you will redirect to.