Try rootless podman networks

[roberth]

NixOS/nixpkgs#125598 (comment), specifically containers/podman#9169

Possible issue containers/podman#10672 (not sure if "internal" network is used)

Ideally it just works and all that's needed is a one or two lines of docs.

[tomprince]

I've succesfully used rootless podman networks with arion[1]. I did need to do a couple of things:

• I want to specify custom network attributes for containers, to set static IP address:

# In a service
{ out.service.networks.${network-name} = { ipv4_address = "192.0.2.1"; } }

• I want to specify configuration for networks and volumes in the compose file:

# top-level
{ docker-compose.raw = {
  networks.${network-name} = { name = "${network-name}"; external = true; };
  volumes.nix = { name = "nix"; external = true; };
}; }

[1] though as my host system isn't nix, I'm just using the nix expression part of arion to generate yaml and images (see #132), which I copy to the host machine.

[roberth]

On NixOS we can use the dnsname plugin. Perhaps it can be used with rootless too somehow? That would be nicer than working with IPs.