Add group information macro for users like $user.local_name$

[Crited]

Is your feature request related to a problem? Please describe.

I'd like to make hosts visible to users based on the group they are part of. Similarly to user.local_name. Given the scenario that a variable like host.vars.contact_groups exists a filter like this would become possible:

host.vars.contact_groups[*]~$user.group_names$

E.g. icingadb/filter/objects

Describe the solution you'd like

Introduce user.group_names to be used in such a filter.

Additional context

Pretty much this for groups: https://icinga.com/docs/icinga-web/latest/doc/06-Security/#username-placeholder
This should also work with Active Directory/LDAP.