Feature request: implement a'la nixos-generators functionality

[unrooted]

Making an .iso file (or any other format) out of currently running system can be helpful.
Especially in case where one wants to use it as on-the-go system and carry their configs and apps everywhere with them. Useful thing when you're forced to work not on your hardware.
Currently, seems like there is such way to do so with nixos-generators. It would be great to integrate such features to your project as well, instead of rewriting flake.nix just for the sake of having an .iso from current system.

[blaggacao]

https://github.com/divnix/devos/blob/01b05551175ba103ea8e2c7682916003ded73f8d/lib/devos/devosSystem.nix#L12-L78

[blaggacao]

I guess we might need some sort of interface into

flake-utils-plus/systemFlake.nix

Line 63 in 51cb739

inputs.nixpkgs.lib.nixosSystem (genericConfigurationBuilder name value)

[blaggacao]

This is now possible in principle (and largely untested in the wilde) through #17.

@unrooted Would you want to consider closing this?

In good onion philosophy, I think an iso feature itself might be rather something for higher level librariss
Es or templates

[unrooted]

Sure, thanks for help!