Email integration

[johnmeshulam]

Description

Closes #1656

In general, the fix is to add a rate-limiting middleware to the affected routes, using a standard library such as express-rate-limit. This middleware will cap how many requests a given client (e.g., IP address) can make within a time window, reducing the risk that repeated CSV uploads or other heavy operations overwhelm the server or database.

For this specific file (apps/backend/src/routers/integrations/sendgrid/index.ts), the best minimal change is:

• Import express-rate-limit.
• Create a small limiter instance configured for admin usage (e.g., a lowish max per 15-minute or per-minute window).
• Apply that limiter as a middleware on the /\:eventId subrouter before the heavy routes, so both /upload-contacts and /send-test are protected, without altering their existing logic, auth, or permissions.

Concretely:

1. Add an import at the top:

   import rateLimit from 'express-rate-limit';

2. Just after creating the router, define an adminLimiter:

   const adminLimiter = rateLimit({
     windowMs: 15 * 60 * 1000, // 15 minutes
     max: 100,                 // limit each IP to 100 requests per windowMs for these routes
     standardHeaders: true,
     legacyHeaders: false
   });

3. Extend the router.use('/:eventId', ...) chain to include this limiter (after auth, so errors will not leak details to unauthenticated users, but before heavy work is done):

   router.use(
     '/:eventId',
     adminAuth,
     adminLimiter,
     attachEvent(),
     requirePermission('MANAGE_EVENT_DETAILS')
   );

This keeps the integration behavior the same for legitimate admins (except for now hitting the configured rate limit if they send excessive requests) and satisfies CodeQL’s concern by explicitly rate-limiting the expensive, authorized handlers.