Guix + User Namespaces wrapper (UGuix)

[Roman Inflianskas <infroma@gmail.com>]

Hello,

I'm writing a wrapper for Guix + User Namespaces called UGuix. The goal is
to implement a tool that would be easy to use and that would provide users
a possibility to install Guix, and then Guix packages without having a
root. It's inspired by https://github.com/nix-community/nix-user-chroot but
aims to be more user-friendly and high-level.

It already works like this:
```
$ ug bootstrap
... # Downloads the binary distribution of Guix, unpacks it to
`~/.guix/root`, does unshare + chroot to the dir with `/gnu` mounted along
with all `/` contents, auths substitutes, downloads latest packages,
installs `hello`
Hello, world!
$ ug run hello  # Runs `hello` installed to `~/.guix/root/gnu`
Hello, world!
$ ug guix install mc
... # Installs mc
```

It works but I want to want to do proper testing before I publish my work.
The question is: is it OK to run the tests which run bootstrap with
downloading packages from substitutes over and over again? Also, I want to
make it so that GitHub Actions will start the tests on new PRs.

-- 
Regards, Roman Inflianskas