⚡ (whatsapp) Improve WhatsApp preview management

Closes #800

apps/builder/src/features/whatsapp/subscribePreviewWebhook.ts

@@ -0,0 +1,30 @@
+import { publicProcedure } from '@/helpers/server/trpc'
+import { TRPCError } from '@trpc/server'
+import { env } from '@typebot.io/env'
+import { z } from 'zod'
+
+export const subscribePreviewWebhook = publicProcedure
+  .meta({
+    openapi: {
+      method: 'GET',
+      path: '/whatsapp/preview/webhook',
+      summary: 'Subscribe webhook',
+      tags: ['WhatsApp'],
+    },
+  })
+  .input(
+    z.object({
+      'hub.challenge': z.string(),
+      'hub.verify_token': z.string(),
+    })
+  )
+  .output(z.number())
+  .query(
+    async ({
+      input: { 'hub.challenge': challenge, 'hub.verify_token': token },
+    }) => {
+      if (token !== env.ENCRYPTION_SECRET)
+        throw new TRPCError({ code: 'UNAUTHORIZED', message: 'Unauthorized' })
+      return Number(challenge)
+    }
+  )