report errorMiddleware errors as unhandled

I found it confusing that unhandled errors caught by the express.js middleware were being reported as handled

This change updates the behavior to match Sentry-Python's Django integration: https://github.com/getsentry/sentry-python/blob/81afcea403c0ac148d631164de29ed80d6a64840/sentry_sdk/integrations/asgi.py#L58

Author: chdsbd

packages/node/src/handlers.ts

@@ -10,6 +10,7 @@ import {
 import type { Span } from '@sentry/types';
 import type { AddRequestDataToEventOptions } from '@sentry/utils';
 import {
+  addExceptionMechanism,
   addRequestDataToTransaction,
   baggageHeaderToDynamicSamplingContext,
   dropUndefinedKeys,
@@ -304,6 +305,11 @@ export function errorHandler(options?: {
           }
         }
 
+        _scope.addEventProcessor(event => {
+          addExceptionMechanism(event, { type: 'middleware', handled: false });
+          return event;
+        });
+
         const eventId = captureException(error);
         // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
         (res as any).sentry = eventId;