feat: Add AfterResponseHook interface

Author: thced

src/main/java/com/retailsvc/http/AfterResponseHook.java

@@ -0,0 +1,22 @@
+package com.retailsvc.http;
+
+/**
+ * Callback invoked after an HTTP response has been written to the client. Runs on the same virtual
+ * thread that handled the request, inside the library's request {@link ScopedValue} binding.
+ *
+ * <p>Hooks fire only when a {@link Request} was successfully constructed — i.e., routing and
+ * parameter/body validation passed. Pre-request failures (404, 405, 400 validation) do not fire
+ * hooks.
+ *
+ * <p>On the error path, {@link Response#body()} is always {@code null} because the body bytes have
+ * already been sent. {@link Response#status()} and {@link Response#headers()} reflect what was
+ * written to the wire.
+ *
+ * <p>Exceptions thrown by a hook are logged at DEBUG and swallowed; subsequent hooks still run.
+ * Hooks compose in registration order.
+ */
+@FunctionalInterface
+public interface AfterResponseHook {
+
+  void after(Request request, Response response);
+}