Use `usercfg.home.username` for username instead of attribute name,
as this way we can change username regardless of the name of the attribute.
(cherry picked from commit 2e13c3cdfd)
When using the NixOS module we cannot guarantee that the Nix store
will be writable during startup. Installing the user packages through
`nix-env -i` will fail in these cases.
This commit adds a NixOS option `home-manager.useUserPackages` that,
when enabled, installs user packages through the NixOS
users.users.<name?>.packages
option.
Note, when submodule support and external package install is enabled
then the installed packages are not available in `~/.nix-profile`. We
therefore set `home.profileDirectory` directly to the HM profile
packages.
This removes the `nixosSubmodule` option in favor of a new option
`submoduleSupport.enable`. This name better indicates that the
submodule mode applies to both NixOS and nix-darwin.
This is a NixOS module that is intended to be imported into a NixOS
system configuration. It allows the system users to be set up directly
from the system configuration.
The actual profile switch is performed by a oneshot systemd unit per
configured user that acts much like the regular `home-manager switch`
command.
With this implementation, the NixOS module does not work properly with
the `nixos-rebuild build-vm` command. This can be solved by using the
`users.users.<name?>.packages` option to install packages but this
does not work flawlessly with certain Nixpkgs packages. In particular,
for programs using the Qt libraries.
