Notification Center aggregation for high‑frequency events

The team wants Notification Center alerts for form submissions to be useful yet non‑intrusive, avoiding a flood of individual emails for each submission.

Notification Center currently delivers each event immediately and lacks a built‑in per‑recipient digest or frequency cap, so the team must decide whether to create a custom gateway/hook for aggregation or accept per‑event notifications.

Key considerations include Contao version compatibility of the extension, the need for a working cron schedule to process queued messages, and the impact on message templates that rely on available tokens.

How should aggregation be implemented without breaking existing templates? Is a per‑user digest queue preferable to time‑based throttling? Which method preserves compatibility across Contao releases?