feat: add a test k3s cluster running on kubevirt

modules/nixos/server/kubevirt-hardware-configuration.nix

@@ -0,0 +1,34 @@
+{modulesPath, ...}:
+##############################################################################
+#
+#  Template for KubeVirt's VM, mainly based on:
+#    https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/virtualisation/kubevirt.nix
+#
+#  We write our hardware-configuration.nix, so that we can do some customization more easily.
+#
+#  the url above is used by `nixos-generator` to generate the KubeVirt's qcow2 image file.
+#
+##############################################################################
+{
+  imports = [
+    "${toString modulesPath}/profiles/qemu-guest.nix"
+  ];
+
+  config = {
+    fileSystems."/" = {
+      device = "/dev/disk/by-label/nixos";
+      fsType = "ext4";
+      autoResize = true;
+    };
+
+    boot.growPartition = true;
+    boot.kernelParams = [ "console=ttyS0" ];
+    boot.loader.grub.device = "/dev/vda";
+    boot.loader.timeout = 0;
+
+    services.qemuGuest.enable = true;
+    services.openssh.enable = true;
+    services.cloud-init.enable = true;
+    systemd.services."serial-getty@ttyS0".enable = true;
+  };
+}