waffentrager: add elements drive service

configurations/host/waffentrager/services/default.nix

@@ -0,0 +1,8 @@
+{ ... }:
+{
+  imports =
+    [
+      ./elements.nix
+    ];
+  waffentragerService.elements.enable = true;
+}

configurations/host/waffentrager/services/elements.nix

@@ -0,0 +1,30 @@
+{ materusArg, config, lib, pkgs, ... }:
+{
+  options.waffentragerService.elements.enable = materusArg.pkgs.lib.mkBoolOpt false "Enable elements drive";
+  options.waffentragerService.elements.path = lib.mkOption { default = "/var/lib/elements"; };
+  options.waffentragerService.elements.uuid = lib.mkOption { default = "e32039c6-e98d-44b0-8e7d-120994bf7be1"; };
+
+  config =
+    let
+      cfg = config.waffentragerService.elements;
+    in
+    lib.mkIf cfg.enable {
+
+      systemd.services.elements-mount = {
+        wantedBy = [ "multi-user.target" ];
+        path = [ pkgs.cryptsetup pkgs.coreutils pkgs.util-linux ];
+        serviceConfig.Type = "oneshot";
+        serviceConfig.RemainAfterExit = true;
+        script = ''
+          mkdir -p ${cfg.path}
+          cryptsetup luksOpen /dev/disk/by-uuid/${cfg.uuid} elements -d ${config.sops.secrets.elements.path}
+          mount /dev/mapper/elements ${cfg.path}
+        '';
+        preStop = ''
+          umount ${cfg.path}
+          cryptsetup luksClose elements
+        '';
+      };
+
+    };
+}