feat: add response.onFinish method

Closes: #82

src/response.ts

@@ -575,6 +575,17 @@ export class Response extends Macroable {
     }
   }
 
+  /**
+   * Listen for the event the response is written
+   * to the TCP socket.
+   *
+   * Under the hood the callback is registered with
+   * the "https://github.com/jshttp/on-finished" package
+   */
+  onFinish(callback: (err: Error | null, response: ServerResponse) => void) {
+    onFinished(this.response, callback)
+  }
+
   /**
    * Writes headers with the Node.js res object using the
    * response.setHeader method

tests/response.spec.ts

@@ -1510,4 +1510,18 @@ test.group('Response', (group) => {
 
     await supertest(url).get('/')
   })
+
+  test('listen for the event when response finishes', async ({ assert }) => {
+    assert.plan(1)
+
+    const { url } = await httpServer.create((req, res) => {
+      const response = new ResponseFactory().merge({ req, res, encryption, router }).create()
+      response.onFinish(() => {
+        assert.isTrue(true)
+      })
+      res.end()
+    })
+
+    await supertest(url).get('/').expect(200)
+  })
 })