Add redirect parameters on login in statistics service

[dunkOnIT]

Redirect parameters should be present on every login. The absence of this makes the entire process a bit more cumbersome and potentially confusing for people who are not used to the platform.

For example, take this process:

Click on a WCA statistics database query URL
Login required
User logs in
Back to home screen. How do I get to the first screen again?

It is a bit counterintuitive. The same happens for any instance of login.

Originally posted by @GuidoDipietro in thewca/worldcubeassociation.org#6777 (comment)

[campos20]

I'm not sure if this is possible of fixing just in the statistics side. The website needs to support redirecting to an arbitrary address (like statistics...org/database and not just statistics...org) I'll run some tests.