feat(nuxt): Add Http responseHook with waitUntil (#13986)

With
[waitUntil](https://vercel.com/docs/functions/functions-api-reference#waituntil)
the lambda execution continues until all async tasks (like sending data
to Sentry) are done.

Timing-wise it should work like this: `span.end()` -> `waitUntil()` ->
Nitro/Node `response.end()`

The problem in [this
PR](#13895) was that
the Nitro hook `afterResponse` is called to late (after
`response.end()`), so `waitUntil()` could not be added to this hook.

---

Just for reference how this is done in Nitro (and h3, the underlying
http framework):

1. The Nitro `afterResponse` hook is called in `onAfterResponse`

https://github.com/unjs/nitro/blob/359af68d2b3d51d740cf869d0f13aec0c5e9f565/src/runtime/internal/app.ts#L71-L77

2. h3 `onAfterResponse` is called after the Node response was sent (and
`onBeforeResponse` is called too early for calling `waitUntil`, as the
span just starts at this point):

https://github.com/unjs/h3/blob/7324eeec854eecc37422074ef9f2aec8a5e4a816/src/adapters/node/index.ts#L38-L47

- `endNodeResponse` calls `response.end()`:
https://github.com/unjs/h3/blob/7324eeec854eecc37422074ef9f2aec8a5e4a816/src/adapters/node/internal/utils.ts#L58

packages/nuxt/src/server/sdk.ts

@@ -1,7 +1,12 @@
-import { applySdkMetadata, getGlobalScope } from '@sentry/core';
-import { init as initNode } from '@sentry/node';
-import type { Client, EventProcessor } from '@sentry/types';
-import { logger } from '@sentry/utils';
+import { applySdkMetadata, flush, getGlobalScope } from '@sentry/core';
+import {
+  type NodeOptions,
+  getDefaultIntegrations as getDefaultNodeIntegrations,
+  httpIntegration,
+  init as initNode,
+} from '@sentry/node';
+import type { Client, EventProcessor, Integration } from '@sentry/types';
+import { logger, vercelWaitUntil } from '@sentry/utils';
 import { DEBUG_BUILD } from '../common/debug-build';
 import type { SentryNuxtServerOptions } from '../common/types';
 
@@ -14,6 +19,7 @@ export function init(options: SentryNuxtServerOptions): Client | undefined {
   const sentryOptions = {
     ...options,
     registerEsmLoaderHooks: mergeRegisterEsmLoaderHooks(options),
+    defaultIntegrations: getNuxtDefaultIntegrations(options),
   };
 
   applySdkMetadata(sentryOptions, 'nuxt', ['nuxt', 'node']);
@@ -46,6 +52,21 @@ export function init(options: SentryNuxtServerOptions): Client | undefined {
   return client;
 }
 
+function getNuxtDefaultIntegrations(options: NodeOptions): Integration[] {
+  return [
+    ...getDefaultNodeIntegrations(options).filter(integration => integration.name !== 'Http'),
+    // The httpIntegration is added as defaultIntegration, so users can still overwrite it
+    httpIntegration({
+      instrumentation: {
+        responseHook: () => {
+          // Makes it possible to end the tracing span before closing the Vercel lambda (https://vercel.com/docs/functions/functions-api-reference#waituntil)
+          vercelWaitUntil(flushSafelyWithTimeout());
+        },
+      },
+    }),
+  ];
+}
+
 /**
  * Adds /vue/ to the registerEsmLoaderHooks options and merges it with the old values in the array if one is defined.
  * If the registerEsmLoaderHooks option is already a boolean, nothing is changed.
@@ -64,3 +85,16 @@ export function mergeRegisterEsmLoaderHooks(
   }
   return options.registerEsmLoaderHooks ?? { exclude: [/vue/] };
 }
+
+/**
+ * Flushes pending Sentry events with a 2-second timeout and in a way that cannot create unhandled promise rejections.
+ */
+export async function flushSafelyWithTimeout(): Promise<void> {
+  try {
+    DEBUG_BUILD && logger.log('Flushing events...');
+    await flush(2000);
+    DEBUG_BUILD && logger.log('Done flushing events');
+  } catch (e) {
+    DEBUG_BUILD && logger.log('Error while flushing events:\n', e);
+  }
+}