docs: include example for server utilities (#21337)

docs/2.guide/2.directory-structure/1.server.md

@@ -102,6 +102,27 @@ Server routes are powered by [unjs/h3](https://github.com/unjs/h3) which comes w
 
 You can add more helpers yourself inside the `~/server/utils` directory.
 
+For example, you can define a custom handler utility that wraps the original handler and performs additional operations before returning the final response.
+
+**Example:**
+
+```ts [server/utils/handler.ts]
+import type { EventHandler } from 'h3'
+
+export const defineWrappedResponseHandler = (handler: EventHandler) =>
+  defineEventHandler(async (event) => {
+    try {
+      // do something before the route handler
+      const response = await handler(event)
+      // do something after the route handler
+      return { response }
+    } catch (err) {
+      // Error handling
+      return { err }
+    }
+  })
+```
+
 ## Server Types
 
 ::alert{type="info"}