Update to (somewhat?) dendritic pattern

Heavily inspired by https://github.com/Doc-Steve/dendritic-design-with-flake-parts.

> Atomic commits? Never heard of them!

modules/system-settings/i18n-de.nix

@@ -0,0 +1,23 @@
+{
+  flake.modules.nixos.i18n-de = {
+    time.timeZone = "Europe/Berlin";
+
+    # Select internationalisation properties.
+    i18n.defaultLocale = "en_US.UTF-8";
+
+    i18n.extraLocaleSettings = {
+      LC_ADDRESS = "de_DE.UTF-8";
+      LC_IDENTIFICATION = "de_DE.UTF-8";
+      LC_MEASUREMENT = "de_DE.UTF-8";
+      LC_MONETARY = "de_DE.UTF-8";
+      LC_NAME = "de_DE.UTF-8";
+      LC_NUMERIC = "de_DE.UTF-8";
+      LC_PAPER = "de_DE.UTF-8";
+      LC_TELEPHONE = "de_DE.UTF-8";
+      LC_TIME = "de_DE.UTF-8";
+    };
+
+    # Configure console keymap
+    console.keyMap = "de";
+  };
+}