refactor: get rid of vars and move common to modules

nixosModules/base/common-nix/default.nix

@@ -0,0 +1,31 @@
+self: {
+  config,
+  lib,
+  ...
+}: let
+  inherit (lib) hasAttr mkIf optionalString;
+
+  inherit (self.inputs) nixpkgs;
+  inherit (config.sops.secrets) access-token;
+
+  cfg = config.roles.base;
+in {
+  config = mkIf cfg.enable {
+    # Minimize dowloads of indirect nixpkgs flakes
+    nix = {
+      registry.nixpkgs.flake = nixpkgs;
+      nixPath = ["nixpkgs=${nixpkgs}"];
+
+      extraOptions =
+        optionalString (hasAttr "sops" config)
+        "!include ${access-token.path}";
+    };
+
+    # Global hm settings
+    home-manager.useGlobalPkgs = true;
+    home-manager.useUserPackages = true;
+  };
+
+  # For accurate stack trace
+  _file = ./default.nix;
+}