Begun yubikey integration

modules/system/security.nix

@@ -2,7 +2,16 @@
   ...
 }:
 {
+  programs = {
+    yubikey-manager.enable = true;
+    yubikey-touch-detector.enable = true;
+  };
+
+  services = {
+    yubikey-agent.enable = true;
+  };
+
   security = {
     rtkit.enable = true;
   };
-}
+}

modules/system/user.nix

@@ -22,6 +22,8 @@
       };
       programs.home-manager.enable = true;
     };
+
+    backupFileExtension = "backup";
   };
 
   users.mutableUsers = false;