Handle multiple messages in a single Meta Cloud API (and Turn.io) webhook payload

[coderabbitai]

Bug: Webhook handlers silently drop all but the first message in a batch

Reported by: @SmittieC
Related PR: #2975
Related comment: #2975 (comment)

Description

The handle_meta_cloud_api_message Celery task (and similarly the Turn.io handler) calls MetaCloudAPIMessage.parse / TurnWhatsappMessage.parse, which is hardcoded to access only the first element of the messages array (messages[0]) in a Meta/Turn.io webhook payload.

According to Meta's API documentation, a single webhook delivery can contain multiple messages. If a webhook delivers a batch of messages, all messages after the first will be silently ignored, leading to data loss without any error or notification.

Affected code

• apps/channels/tasks.py — handle_meta_cloud_api_message
• apps/channels/tasks.py — handle_turn_message
• apps/channels/datamodels.py — MetaCloudAPIMessage.parse / TurnWhatsappMessage.parse

Suggested Fix

Modify the task(s) to iterate over the messages array in the webhook payload and process each message individually, rather than only processing the first one.

Notes

• Deferred from PR Meta Cloud API Whatsapp Integration #2975 to a future PR.
• Existing tests do not cover the multi-message scenario.