Change structure

modules/system/darwin/casks/obsidian.nix

@@ -0,0 +1,17 @@
+{ lib, config, ... }:
+with lib;
+let
+  cfg = config.os.homebrew.obsidian;
+in
+{
+  options.os.homebrew.obsidian = {
+    enable = mkEnableOption "System obsidian homebrew service";
+  };
+  config = mkIf cfg.enable {
+
+    homebrew.casks = [
+      "obsidian"
+    ];
+
+  };
+}