chore(lib/treewide): cleanup directory struture of lib. See lib/readme.md for details

lib/inventory/default.nix

@@ -2,4 +2,41 @@
 {
   inherit (import ./build-inventory { inherit lib clanLib; }) buildInventory;
   interface = ./build-inventory/interface.nix;
+  mapInstances = clanLib.callLib ./distributed-service/inventory-adapter.nix {};
+    # Returns the list of machine names
+  # { ... } -> [ string ]
+  resolveTags =
+    {
+      # Available InventoryMachines :: { {name} :: { tags = [ string ]; }; }
+      machines,
+      # Requested members :: { machines, tags }
+      # Those will be resolved against the available machines
+      members,
+      # Not needed for resolution - only for error reporting
+      roleName,
+      instanceName,
+    }:
+    {
+      machines =
+        members.machines or [ ]
+        ++ (builtins.foldl' (
+          acc: tag:
+          let
+            # For error printing
+            availableTags = lib.foldlAttrs (
+              acc: _: v:
+              v.tags or [ ] ++ acc
+            ) [ ] (machines);
+
+            tagMembers = builtins.attrNames (lib.filterAttrs (_n: v: builtins.elem tag v.tags or [ ]) machines);
+          in
+          if tagMembers == [ ] then
+            lib.warn ''
+              Service instance '${instanceName}': - ${roleName} tags: no machine with tag '${tag}' found.
+              Available tags: ${builtins.toJSON (lib.unique availableTags)}
+            '' acc
+          else
+            acc ++ tagMembers
+        ) [ ] members.tags or [ ]);
+    };
 }