Switch user targetUrl config to redirect after login/logout

### Feature description

Hi, I was wondering if it's possible to add two new parameters to set a targetUrl to redirect after login and logout. Something like:

`grails.plugin.springsecurity.switchUser.afterLoginTargetUrl`
`grails.plugin.springsecurity.switchUser.afterLogoutTargetUrl`

This configurations are only to customize that behaviour, otherwise the plugin takes the value of: `grails.plugin.springsecurity.switchUser.targetUrl`

If it's possible, just point me the right direction and I will make a PR.

No file or test is named in the issue. Locate the switch-user implementation and existing targetUrl configuration, then trace the login and logout redirect paths; done means separate after-login and after-logout settings override the shared targetUrl while retaining it as the fallback.

Written by the indexing model from the issue text.