Avoid possible infinite recursion

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/user/configs/gui/swww/default.nix

@@ -1,5 +1,5 @@
 {
-  user ? throw "user argument is required",
+  username ? throw "username argument is required",
 }:
 {
   config,
@@ -8,7 +8,8 @@
   ...
 }:
 let
-  hmConfig = config.home-manager.users.${user.name};
+  userConfig = config.users.users.${username};
+  hmConfig = config.home-manager.users.${username};
   themeSwww = lib.meta.getExe (
     pkgs.writeShellApplication {
       name = "theme-swww";
@@ -21,10 +22,10 @@ let
   );
 in
 {
-  home-manager.users.${user.name} = {
+  home-manager.users.${username} = {
     home = {
       packages = with pkgs; [ swww ];
-      persistence."/cache${user.home}".directories = [ "${hmConfig.xdg.relativeCacheHome}/swww" ];
+      persistence."/cache${userConfig.home}".directories = [ "${hmConfig.xdg.relativeCacheHome}/swww" ];
     };
 
     systemd.user.services.swww = {