…307)

Fixes #304 
Unblocks #298 

After logging in, the login flow should redirect to a whatever path is specified by the `?redirect` query parameter. This is important for cases like #298 - where we need to set `?redirect=%2Fcli_auth`, but also really any case where the user is linked and might have to go back to the login screen.

The fix is simple - just check if the `redirect` query parameter is set, and if it is, use that as the path to redirect to on success. Also adds a test case - we had one checking that we redirect to the default (root `/`) url, but not one of the `?redirect` param