fix(nix): remove flattenAttrs

unfortunately modules don't like to be merged

nix/configurations.nix

@@ -6,7 +6,6 @@
 }:
 let
   inherit (lib) nixosSystem;
-  inherit (cfg.lib) flattenAttrs;
   inherit (lib.attrsets) mapAttrs;
   cfg = config.flake;
   hosts = cfg.manifest.hosts or { };
@@ -22,7 +21,7 @@ let
             hostName = name;
           };
           modules = [
-            (flattenAttrs cfg.modules.nixos)
+            cfg.modules.nixos.default
             (value.extraCfg or { })
           ];
         }

nix/lib/default.nix

@@ -1,36 +1,10 @@
 { lib, config, ... }:
 let
   cfg = config.flake;
-  inherit (lib.attrsets) mapAttrs concatMapAttrs;
+  inherit (lib.attrsets) mapAttrs;
 in
 {
   flake.lib = {
-    /**
-      Remove the top level attributes from an attribute set and return the merged attributes.
-
-      # Inputs
-
-      `attrset`
-
-      : An attribute set to flatten.
-
-      # Type
-
-      ```
-      flattenAttrs :: AttrSet -> AttrSet
-      ```
-
-      # Examples
-      :::{.example}
-      ## `flattenAttrs` usage example
-
-      ```nix
-      flattenAttrs { x = { a = 1; b = 2; }; y = { c = 3; d = 4; }; }
-      => { a = 1; b = 2; c = 3; d = 4; }
-      ```
-    */
-    flattenAttrs = attrset: concatMapAttrs (_: v: v) attrset;
-
     /**
       Return an attribute set for use with a option that needs to be used for all users.
 

nix/modules/home-manager.nix

@@ -1,15 +1,13 @@
 { inputs, config, ... }:
 let
-  inherit (cfg.lib) forAllUsers' flattenAttrs;
+  inherit (cfg.lib) forAllUsers';
   cfg = config.flake;
   hm = inputs.home-manager;
   globalCfg = {
     useGlobalPkgs = true;
     useUserPackages = true;
     extraSpecialArgs = { inherit (cfg) manifest; };
-    sharedModules = [
-      (flattenAttrs (cfg.modules.homeManager or { }))
-    ];
+    sharedModules = [ cfg.modules.homeManager.default ];
     users = forAllUsers' (name: _: cfg.homes.${name});
   };
 in