feat: add test code to assert if k3s is running

clanServices/zitadel/default.nix

@@ -77,6 +77,21 @@ in
         };
       in
       {
+        assertions = 
+        let
+          inherit (lib) attrValues any;
+        in
+        [
+          {
+            assertion = 
+              config.services.k3s.enable == true;
+              # config.clan.inventory.instances
+              # |> attrValues
+              # |> any ({ module, ... }: module.name == "k3s");
+            message = "This module requires k3s in order to run";
+          }
+        ];
+
         clan.core.vars.generators.zitadel = {
           share = false;