nixos/state: init module

modules/nixos/_private/default.nix

@@ -1,6 +1,7 @@
 {
   imports = [
     ./extra-arguments.nix
+    ./state.nix
     ./suites/archiving.nix
     ./suites/browsers.nix
     ./suites/desktop.nix

modules/nixos/_private/state.nix

@@ -0,0 +1,25 @@
+{ lib, ... }:
+
+{
+  options.state = lib.mkOption {
+    type = lib.types.submodule {
+      freeFormType = with lib.types; attrsOf anything;
+      default = { };
+    };
+    description = ''
+      A set of values referring to the system state for use in other parts of
+      the NixOS system. Useful for consistent values and referring to a single
+      source of truth for different parts (e.g., services, program) of the
+      system.
+    '';
+    example = {
+      services = {
+        postgresql.directory = "/var/lib/postgresql";
+        backup.ignoreDirectories = [
+          "node_modules"
+          ".direnv"
+        ];
+      };
+    };
+  };
+}