Support generating quadlet configuration

Hi,

latest versions of podman support so called "quadlets" (see manpage podman-systemd.unit(5) or quadlet(5) ), which is an autogeneration of systemd units from container definitions, volume definitions or kube definitions to play kube files like for podman kube play.

Former versions of podman-compose were using pods to create a composition of containers, but, as far as I understand, recent versions use a bridge network, and creating pods has been seen just as a workaround until podman-compose was able to properly create bridge networks.

The advantage of pods was, that
`podman generate kube podname`
was able to directly generate such a kube file from a running pod, created by podman-compose, while this doesn't work for bridge based compositions.

It would be highly useful if podman-compose could support creating such kube files to have systemd start a container composition just like podman-compose, but with a kube file, in either way. Either have an option to create an old-fashioned pod instead of a bridge network, as former versions did, or something else.

What was, btw., the reason to drop support for pods in favour of bridges, and not keeping both as options?

regards

Start with podman-systemd.unit(5), quadlet(5), and the existing podman-compose behavior around bridge networks and pod creation. Resolve whether the feature should generate quadlet or kube files, restore an option for pods, or support both; done means a composition can be started by systemd using the selected approach.

Written by the indexing model from the issue text.