Add a monoid to lib that merges objects together

lib/default.nix

@@ -1,2 +1,29 @@
 lib: {
+  hylonix = {
+    recursiveMerge =
+      let
+        f =
+          x: y:
+          if y == null then
+            x
+          else if builtins.typeOf x != builtins.typeOf y then
+            y
+          else if builtins.typeOf x == "set" then
+            builtins.listToAttrs (
+              builtins.map (name: {
+                inherit name;
+                value = f (x.${name} or null) (y.${name} or null);
+              }) (builtins.attrNames y ++ builtins.attrNames x)
+            )
+          else if builtins.typeOf x == "list" then
+            x ++ y
+          else
+            y;
+      in
+      f;
+
+    recursiveMergeAll = builtins.foldl' lib.hylonix.recursiveMerge null;
+  };
+
+  inherit (lib.hylonix) recursiveMerge recursiveMergeAll;
 }