flake.nix: provide flake with access to the nixos-container nixos module

[Cynerd]

This allows simple inclusion and update of the vpsadminos configuration to the third-party containers.

The example usage in my repository https://git.cynerd.cz/nixos-personal/tree/flake.nix#n55.

[aither64]

I have merged it, but fixed a few nits + I renamed nixosConfigurations.default to nixosConfigurations.container. Is that going to work? In our case, the default would make sense for building vpsAdminOS itself using flakes. I'm not familiar with flakes myself, so I hope it could work like this.

[Cynerd]

Is that going to work? In our case, the default would make sense for building vpsAdminOS itself using flakes. I'm not familiar with flakes myself, so I hope it could work like this.

It can work like this. It is expected that there is at least default in output, but here you are right that it is not exactly correct here. You might get around using flakes later on so it makes sense to keep default undefined here for sure.

[aither64]

Great, thanks :)