Sophisticated access control per user per helpdesk

To fulfill this requirement, we want to use ECA, so we have to add an event when the users get synchronized. If that is in place, we can create an ECA model, which determines which helpdesk should be used.

Currently, the default helpdesk is used in any cases.

Yeah, but not only for user sync. This is necessary for each function where the helpdesk gets selected, e.g. when going to /helpdesk or when creating a new issue.

So, the event should be dispatched when the helpdesk entity gets loaded. That should then be affecting user sync and all the other places as well.