Feature request: install for a single user which is not root

[noamraph]

In many cases (WSL for example) I have sudo permissions, and I intend to use nix only from a single user. Then the simplest installation is to use sudo just to create the /nix directory and make it owned by the active user, and then do everything else rootless, and without a service.

The classic installer supports this - it is what you get if you download the nix tar and just run ./install.

Can nix-installer support it too?