Plugin audit log on events

[mariusandra]

Currently if for example one export plugin stops working (export server throws 500), the plugin is ignored and we won't know what event it is unless we do a full diff for event IDs in both posthog and the export destination.

There should be an easier way. Building support for retries (comment below the line here, internal discussion) would solve this, however just keeping a history of what plugins were applied to an event will give us enough information to make due in case of emergency.

I imagine we will just set a property on the ingested event, something like event.properties['$plugins_ran'] = [] and event.properties['$plugins_failed'] = [] and then push something to those arrays after plugins run. For example event.properties['$plugins_failed'].push(${plugin.id}-${toSlug(plugin.name)}`)...

This has not been asked by any user yet, though it might be useful to implement regardless.

[Twixes]

I think this was addressed in #327.