Webhook calls are duplicated in Confluence Cloud

Issue Summary

On some Confluence cloud instances, the webhook calls (listener-triggered, app-data-uploaded) are duplicated several times and repeated over a period of three days.

Steps to Reproduce

This does not happen with all Confluence Cloud instances.

1. Register your Connect app for webhooks in the Notification API
2. Perform a migration
3. Ensure a 2xx return is made within 10 seconds of receiving the webhook

Expected Results

The webhook is called only once.

Actual Results

The webhook (both listener-triggered and if included app-data-uploaded) are called at least once.

Workaround

As documented in Definitions of event attributes each webhook has a unique messageId, which can be used to confirm if a webhook message has already been received.