feat(xatu): construct lexical scope graphs

src/xatu/testdata/clean.nix

@@ -1,6 +1,19 @@
 { pkgs }:
-
+let
+  render = value:
+    let
+      normalized = normalize value;
+      inherit value;
+      inherit (pkgs) prefix;
+    in
+    assert normalized != null;
+    { ${normalized} = "${prefix}${normalized}"; };
+  normalize = value: if value == null then fallback else value;
+  fallback = "default";
+  project = { value, normalize ? value }@args: { inherit (args) value; extra = normalize; };
+in
 {
+  result = render (project { value = "name"; }).value;
   path = ./. + "/foo";
   url = "https://example.com";
   inherit pkgs;