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/config.nix

@@ -15,10 +15,10 @@
   };
   config = {
     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; };
     in lib.mkMerge (map (user: {
       ${user}.shell = pkgs.${config.my.shell.type};
-    }) users);
+    }) (userLib.normalizeUsers config.my.toggleUsers.shell));
     programs.zsh.enable = config.my.shell.type == "zsh";
   };
 }

modules/shell/exercism.nix

@@ -8,15 +8,13 @@
   options.my.shell.exercism.enable = lib.mkEnableOption "Exercism coding practice platform";
   config = lib.mkIf config.my.shell.exercism.enable {
     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)
-        exercism # learn to code
-        bats # testing system, required by Exercism
-        ;
+        inherit (pkgs)
+          exercism # learn to code
+          bats # testing system, required by Exercism
+          ;
       };
-    in lib.mkMerge (map (user: {
-      ${user}.packages = packages;
-    }) users);
+    in userLib.mkUserPackages config.my.toggleUsers.shell packages;
   };
 }

modules/shell/multimedia.nix

@@ -9,17 +9,18 @@
   options.my.shell.multimedia.enable = lib.mkEnableOption "multimedia CLI tools and codecs";
   config = lib.mkIf config.my.shell.multimedia.enable {
     sops.secrets."gallery-dl/secrets" = let
+      userLib = import ../lib.nix { inherit lib; };
       # Use first user for secret ownership
-      user = if lib.isString config.my.toggleUsers.shell then config.my.toggleUsers.shell else (lib.head config.my.toggleUsers.shell);
+      user = userLib.getFirstUser config.my.toggleUsers.shell;
     in {
       sopsFile = ../../secrets/gallery.yaml;
       owner = user;
       mode = "0400";
     };
     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 = {
         yt-dlp = {
           enable = true;
           settings = {
@@ -43,18 +44,16 @@
           '';
         };
       };
-    }) users);
+    });
     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)
-        ffmpeg # not ffmpreg, the coolest video conversion tool!
-        imagemagick # photoshop what??
-        ffpb # make ffmpeg encoding... a bit fun
-        ;
+        inherit (pkgs)
+          ffmpeg # not ffmpreg, the coolest video conversion tool!
+          imagemagick # photoshop what??
+          ffpb # make ffmpeg encoding... a bit fun
+          ;
       };
-    in lib.mkMerge (map (user: {
-      ${user}.packages = packages;
-    }) users);
+    in userLib.mkUserPackages config.my.toggleUsers.shell packages;
   };
 }

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 = "-";