avahi-gobject: ga_entry_group_add_service_full is not introspectable

[smspillaz]

It'd be nice if we could use this from language bindings, but it is not introspectable for now because both it and ga_entry_group_add_service_full_strlist are not marked introspect able, possibly because they return the unboxed struct type GaEntryGroupService.

It'd be nice to box that / provide a way to wrap it in a GObject so that it could be used from bindings.

[pemensik]

Just tried command busctl tree org.freedesktop.Avahi and indeed it does not expose much. We want DBus to become primary way of communicating from less common languages. Good and nice dbus introspection should make working with it much easier.