This is the same as the feature already present in the launcher and
connection settings. Not sure how much sense it makes for systemd services
as they run rather independently from the UI but maybe it is useful.
* Allow to pause all devices on metered network connections (devices will
be automatically resumed when network is no longer metered)
* Allow to stop Syncthing when it was started via the built-in launcher
on metered network connections (it will be automatically started again
when the network connection is no longer metered)
* See https://github.com/Martchus/syncthingtray/issues/231
Martchus