Quadlets by default when stopped don't keep a container around which means cockpit-podman can't display them out of the box.

To implement showing them cockpit-podman will have to parse the podman-systemd-generated .service files in /run/systemd/generator and /run/user/1000/systemd/generator as systemd provides no API for this as of yet.

The idea is to merge these quadlets into the existing containers / pods state and change the unique key to "uid-myunit.service" (by changing `makeKey`). Then show them as stopped/failed containers so eventually we can start/restart/stop them with `systemctl` in cockpit-podman.

The systemd unit state would need to be separately queried and optionally we could discover the mountpoints/volumes, and portmappings from the .container/.pod files.