"Grouped" CDP notifications / stages

[joesaunderson]

Feature request

Is your feature request related to a problem?

We really like the CDP feature, we're using it to send notifications to Slack.

However, it's noisy sometimes...

Describe the solution you'd like

The ability to "group" batches of events, and send notifications in chunks... for example, we currently send a notification every time someone uploads an image... instead:

"52 people uploaded images in the last hour"

or

"1580 uploaded images yesterday"

The interesting part would be how we group... the example above would be all, but it would be good to be able to group by group / user / some other property instead, so:

"26 people from X uploaded in an image in the last hour"

Describe alternatives you've considered

Not using PostHog, and investing in Knock or similar... but that's cost!

Additional context

N/A

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]