refactor: Use haumea for filesystem-based module system for flake outputs

refactor: Use hyphen(`-`) for variable names & folder names(except Python), replace all unserscore(`_`) with hyphen(`-`).

hosts/k8s/k3s-prod-1-master-1/k3s.nix

@@ -0,0 +1,42 @@
+{
+  config,
+  pkgs,
+  myvars,
+  ...
+}: let
+  package = pkgs.k3s_1_29;
+in {
+  environment.systemPackages = with pkgs; [
+    package
+    k9s
+    kubectl
+    istioctl
+    kubernetes-helm
+
+    skopeo
+    dive # explore docker layers
+  ];
+  services.k3s = {
+    inherit package;
+    enable = true;
+
+    # Initialize HA cluster using an embedded etcd datastore.
+    # If you are configuring an HA cluster with an embedded etcd,
+    # the 1st server must have `clusterInit = true`
+    # and other servers must connect to it using serverAddr.
+    clusterInit = true;
+    role = "server";
+    tokenFile = config.age.secrets."k3s-prod-1-token".path;
+    # https://docs.k3s.io/cli/server
+    extraFlags =
+      " --write-kubeconfig /home/${myvars.username}/.kube/config"
+      + " --write-kubeconfig-mode 644"
+      + " --service-node-port-range 80-32767"
+      + " --kube-apiserver-arg='--allow-privileged=true'" # required by kubevirt
+      + " --node-taint=CriticalAddonsOnly=true:NoExecute" # prevent workloads from running on the master
+      + " --data-dir /var/lib/rancher/k3s"
+      + " --disable-helm-controller"
+      + " --etcd-expose-metrics true"
+      + ''--etcd-snapshot-schedule-cron "0 */12 * * *"'';
+  };
+}