meta: Add network example

This is a working example of using the modules in our existing
configuration to start a network of virtual machines with
nixos-build-vms. Note that VMs take longer to start up in this case than
nixos-rebuild build-vm, and that said VMs may lack certain functionality
(such as dynamic resolution in GNOME) that would otherwise be present
with build-vm.

Although networks are certainly cute (and I'm glad that I feel familiar
with them thanks to my better understanding of Nix), they do seem less
convenient than nixos-rebuild build-vm and don't appear to support Nix
flakes. Networks therefore seem more useful for running multiple one-off
services that couldn't otherwise be ran in a container.

modules/default.nix

@@ -10,5 +10,12 @@
     ./starship.nix
     ./stylix.nix
     ./thunar.nix
+    ./user.nix
   ];
+
+  virtualisation.vmVariant = {
+    imports = [
+      ./virtualization.nix
+    ];
+  };
 }

modules/user.nix

@@ -0,0 +1,12 @@
+let VARIABLES = import ../src/variables.nix; in {
+  users = {
+    mutableUsers = false;
+
+    users."${VARIABLES.username}" = {
+      isNormalUser = true;
+      uid = 1000;
+      password = "user";
+      extraGroups = [ "wheel" "networkmanager" ];
+    };
+  };
+}

modules/virtualization.nix

@@ -0,0 +1,17 @@
+{
+  virtualisation = {
+    memorySize = 8192;
+    cores = 4;
+  };
+
+  virtualisation.qemu.options = [
+    "-device virtio-vga-gl"
+    "-display sdl,gl=on,show-cursor=off"
+    "-full-screen"
+    "-audio pa,model=hda"
+  ];
+
+  environment.sessionVariables = {
+    WLR_NO_HARDWARE_CURSORS = "1";
+  };
+}

networks/default.nix

@@ -0,0 +1,16 @@
+{
+  plasma = {
+    imports = [
+      ../modules/virtualization.nix
+      ../modules/user.nix
+      ../modules/plasma.nix
+    ];
+  };
+  gnome = {
+    imports = [
+      ../modules/virtualization.nix
+      ../modules/user.nix
+      ../modules/gnome.nix
+    ];
+  };
+}

src/main.nix

@@ -194,16 +194,6 @@ let VARIABLES = import ./variables.nix; in {
   time.timeZone = "${VARIABLES.timezone}"; # Timezone
 
   # user
-  users = {
-    mutableUsers = false;
-
-    users."${VARIABLES.username}" = {
-      isNormalUser = true;
-      uid = 1000;
-      password = "user";
-      extraGroups = [ "wheel" "networkmanager" ];
-    };
-  };
 
   home-manager.users.user = {
     home.username = VARIABLES.username;
@@ -229,20 +219,6 @@ let VARIABLES = import ./variables.nix; in {
 
   systemd.services.NetworkManager-wait-online.enable = false;
 
-  # virtualization
-  virtualisation.vmVariant = {
-    virtualisation = {
-      memorySize = 8192;
-      cores = 4;
-    };
-
-    virtualisation.qemu.options = [ "-device virtio-vga-gl" "-display sdl,gl=on,show-cursor=off" "-full-screen" "-audio pa,model=hda" ];
-
-    environment.sessionVariables = {
-      WLR_NO_HARDWARE_CURSORS = "1";
-    };
-  };
-
   # mullvad-vpn
   services.mullvad-vpn = {
     enable = true;