Inventory: init inventory.tags for globally defined static and dynamic tags

lib/build-clan/computed-tags.nix

@@ -0,0 +1,33 @@
+{
+  config,
+  lib,
+  ...
+}:
+{
+  config.inventory = {
+    tags = (
+      { machines, ... }:
+      {
+        # Only compute the default value
+        # The option MUST be defined in ./build-inventory/interface.nix
+        all = lib.mkDefault (builtins.attrNames machines);
+      }
+    );
+  };
+  # Add the computed tags to machine tags for displaying them
+  options.inventory = {
+    machines = lib.mkOption {
+      type = lib.types.attrsOf (
+        lib.types.submodule (
+          # 'name' is the machines attribute-name
+          { name, ... }:
+          {
+            tags = builtins.attrNames (
+              lib.filterAttrs (_t: tagMemers: builtins.elem name tagMemers) config.inventory.tags
+            );
+          }
+        )
+      );
+    };
+  };
+}

lib/build-clan/module.nix

@@ -162,6 +162,8 @@ in
     #
     # config.inventory.meta <- config.meta
     { inventory.meta = config.meta; }
+    # Set default for computed tags
+    ./computed-tags.nix
   ];
 
   inherit nixosConfigurations;