Add helper functions for multi-user toggle support

Introduced a new file `lib.nix` containing helper functions to streamline user package management and attributes for multi-user configurations. Updated various modules to utilize these functions, enhancing code maintainability and readability.

modules/shell/tools.nix

@@ -12,9 +12,9 @@ in
   options.my.shell.tools.enable = lib.mkEnableOption "shell tools and utilities";
   config = lib.mkIf config.my.shell.tools.enable {
     home-manager.users = let
-      users = if lib.isString config.my.toggleUsers.shell then [ config.my.toggleUsers.shell ] else config.my.toggleUsers.shell;
-    in lib.mkMerge (map (user: {
-      ${user}.programs = {
+      userLib = import ../lib.nix { inherit lib; };
+    in userLib.mkHomeManagerUsers config.my.toggleUsers.shell (user: {
+      programs = {
       hstr.enable = true;
       htop = {
         enable = true;
@@ -88,7 +88,7 @@ in
             fi
           '';
       };
-    }) users);
+    });
     programs = {
       starship.enable = true;
       tmux.enable = true;
@@ -99,7 +99,7 @@ in
       };
     };
     users.users = let
-      users = if lib.isString config.my.toggleUsers.shell then [ config.my.toggleUsers.shell ] else config.my.toggleUsers.shell;
+      userLib = import ../lib.nix { inherit lib; };
       packages = builtins.attrValues {
       inherit (pkgs)
         ripgrep # modern grep
@@ -115,9 +115,7 @@ in
         rmlint # amazing dupe finder that integrates well with BTRFS
         ;
       };
-    in lib.mkMerge (map (user: {
-      ${user}.packages = packages;
-    }) users);
+    in userLib.mkUserPackages config.my.toggleUsers.shell packages;
     environment.variables = {
       HISTFILE = "\${XDG_STATE_HOME}/bash/history";
       LESSHISTFILE = "-";