According to documentation [1] a menu item has a target attribute, which is "the parameter to pass when activating the action".
Furthermore, the action "Activate" method specifies "If the action activation requires a parameter then this parameter must
be given in the second parameter (av).". Also implements a TODO in the code.
[1] https://wiki.gnome.org/Projects/GLib/GApplication/DBusAPI
CCBUG: 418385
Differential Revision: https://phabricator.kde.org/D27884
This way we can monitor both appmenu and window menu simultaneously and (theoretically)
switch between one and the other on the fly.
The Menu class is now Window as it encapsulates an entire window with everything that belongs to it.
All DBusMenu-specific code is in Window whereas GMenu-stuff is in Menu and so it's less entangled