feat(arns): disable ArNS and sandboxing if ARNS_ROOT_HOST is unset

Disables the ArNS and sandbox middlewares if ARNS_ROOT_HOST is not set.
This reduces potential routing annoyances when testing without Envoy
(not a recommended production setup).

src/app.ts

@@ -79,19 +79,21 @@ const dataHandler = createDataHandler({
   manifestPathResolver: system.manifestPathResolver,
 });
 
-app.use(
-  createArnsMiddleware({
-    dataHandler,
-    nameResolver: system.nameResolver,
-  }),
-);
-
-app.use(
-  createSandboxMiddleware({
-    rootHost: config.ARNS_ROOT_HOST,
-    sandboxProtocol: config.SANDBOX_PROTOCOL,
-  }),
-);
+if (config.ARNS_ROOT_HOST !== undefined) {
+  app.use(
+    createArnsMiddleware({
+      dataHandler,
+      nameResolver: system.nameResolver,
+    }),
+  );
+
+  app.use(
+    createSandboxMiddleware({
+      rootHost: config.ARNS_ROOT_HOST,
+      sandboxProtocol: config.SANDBOX_PROTOCOL,
+    }),
+  );
+}
 
 // OpenAPI Spec
 const openapiDocument = YAML.parse(