Fix FOSS webhook, update actions calculation

[yakkomajuri]

Changes

Works in conjunction with PostHog/plugin-server#233

On PostHog FOSS:

• Calculates actions for an event when that event is ingested rather than instance-wide periodically
• Triggers the webhook after the calculation if the event should trigger a webhook

Discussion about the approach on Slack.

Checklist

• All querysets/queries filter by Organization, by Team, and by User
• Django backend tests
• Jest frontend tests
• Cypress end-to-end tests

[mariusandra]

The code seems fine for me, but at the end of the day, this comment (added here) still scares me:

(and this PR removes this comment)

Sure it's not "sync" anymore, but we'll be doing action matching in "unbatched-async", which is different from "batched-async". Without any performance tests, we could break heavy volume OSS users with so many potentially difficult queries running in parallel.

Or it could be perfectly fine, but I'm just not sure and afraid of again breaking some setups...

Here's an alternative way to do this entire action matching though: PostHog/plugin-server#235

[Twixes]

Is this still applicable after recent merges?

[mariusandra]

I think not. And given what we discussed on slack, running a catch-all action.calculate_events(start=action.last_calculated_at) for every event is probably a recipe for deadlocks and funny business.