flake-parts/setups: add firstSetupArgs option for generic config environment

configs/flake-parts/home-manager.nix

@@ -31,19 +31,14 @@
         };
         homeManagerBranch = "home-manager-unstable";
         systems = [ "aarch64-linux" "x86_64-linux" ];
+        firstSetupArgs = {
+          baseNixvimModules = config.setups.nixvim.configs.fiesta.modules
+            ++ config.setups.nixvim.sharedModules;
+        };
         modules = [
           inputs.nur.modules.homeManager.default
           inputs.sops-nix.homeManagerModules.sops
           inputs.wrapper-manager-fds.homeModules.wrapper-manager
-
-          {
-            _module.args = {
-              firstSetupArgs = {
-                baseNixvimModules = config.setups.nixvim.configs.fiesta.modules
-                  ++ config.setups.nixvim.sharedModules;
-              };
-            };
-          }
         ];
         nixvim = {
           instance = "fiesta";

modules/flake-parts/setups/shared/config-options.nix

@@ -30,5 +30,30 @@
         of the same declarative environment.
       '';
     };
+
+    firstSetupArgs = lib.mkOption {
+      type = with lib.types; attrsOf anything;
+      default = {};
+      example = lib.literalExpression ''
+        {
+          baseSpecificConfigModules = [
+            ./whatwhatwut/base.nix
+          ];
+        }
+      '';
+      description = ''
+        A set of module arguments intended to be set as part of the module
+        argument namespace `firstSetupArgs` in the configuration.
+
+        :::{.note}
+        Functionally similar to {option}`specialArgs` but only different in
+        intent and also for organization purposes.
+        :::
+      '';
+    };
+  };
+
+  config.modules = lib.singleton {
+    _module.args = { inherit (config) firstSetupArgs; }
   };
 }