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 theredirect 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