Restructure Darwin configuration

So far, this is just based on mightymac. The other devices will be
updated soon.

lib/default.nix

@@ -2,10 +2,6 @@
   mkDarwinHost = import ./mkDarwinHost.nix { inherit inputs; };
   mkNixosHost = import ./mkNixosHost.nix { inherit inputs; };
 in {
-  inherit (mkDarwinHost)
-    mkDarwinHost
-    ;
-  inherit (mkNixosHost)
-    mkNixosHost
-    ;
-}
+  inherit (mkDarwinHost) mkDarwinHost;
+  inherit (mkNixosHost) mkNixosHost;
+}

lib/mkDarwinHost.nix

@@ -26,13 +26,13 @@
           useUserPackages = true;
           users.${username}.imports = [
             inputs.sops-nix.homeManagerModule # user-level secrets management
-            ../modules/home-manager/hosts/${hostname}/${username}.nix 
+            ../modules/hosts/darwin/${hostname}/${username}.nix 
           ];
         };
       }
 
-      ../modules/system/common/all-darwin.nix # system-wide stuff
+      ../modules/hosts/darwin # system-wide stuff
       ../modules/hosts/darwin/${hostname} # host specific stuff
     ] ++ additionalModules; # end modules
   }; # end darwinSystem
-}
+}

lib/mkNixosHost.nix

@@ -31,4 +31,4 @@
       ../modules/hosts/nixos/${hostname} # host specific stuff
     ] ++ additionalModules;
   };
-}
+}