put locales in a module

modules/nix/locales.nix

@@ -0,0 +1,14 @@
+{ config, lib, pkgs, ... }:
+{
+  i18n.defaultLocale = "en_US.UTF-8";
+  i18n.extraLocaleSettings = {
+    LC_ADDRESS = "fr_FR.UTF-8";
+    LC_IDENTIFICATION = "fr_FR.UTF-8";
+    LC_MEASUREMENT = "fr_FR.UTF-8";
+    LC_MONETARY = "fr_FR.UTF-8";
+    LC_NAME = "fr_FR.UTF-8";
+    LC_NUMERIC = "fr_FR.UTF-8";
+    LC_PAPER = "fr_FR.UTF-8";
+    LC_TELEPHONE = "fr_FR.UTF-8";
+  };
+}