[Feature request] support nftables

[Mr-win7]

The work is really impressed!

When I'm planning to apply it into my mac with podman, I notice that podman machine use nftables, not the iptables.

I notice that main logic about iptables is implemented in

wag/internal/router/iptables.go

Line 172 in e2e649f

func (f *Firewall) teardownIptables() {

, could we create an abstract interface and make the program both compatible with nftables and iptables.

I also notice that

wag/Dockerfile

Line 24 in e2e649f

microdnf install -y iptables nc pam && \

is trying to install the dependencies, maybe need some extra logic to detect the dependencies in the machine or some settings to determine which to use.

I'm glad to help implement it or test in my stack.

[NHAS]

Yep! Good point, I've been thinking about adding/change this over for years at this point now that iptables is on the way out. Shouldnt be too much of a challenge, but at the moment reasonably busy so no promises on timing :)