A monitor spec object is meant to be used to identify a certain monitor
on a certain output. The spec is unique per actual monitor and connector,
meaning that a monitor that changes from one connector from another
(e.g. HDMI1 to HDMI2) will not be identified as the same. It is meant
to associate for example a configuration entry with an actual monitor.
https://bugzilla.gnome.org/show_bug.cgi?id=777732