feat: add subuid and subgid to ease up use of podman

[areitz86]

Rootless Podman requires users to have set up subuids and subgids. This can be done in multiple ways.
If the files /etc/subuid and /etc/subgid exist, useradd defaults to adding those ranges (see [1]). Those files seem to exist (checked fedora flavor). Yip/entities have not implemented this. Maybe this could be a configurable field in the user map?

[1] https://manpages.ubuntu.com/manpages/jammy/en/man8/useradd.8.html

[jimmykarily]

This makes sense @areitz86 but I'm not sure when we'll have time to look into it. We'll keep it in the backlog and discuss it in the future planning calls. Stay tuned.