Make the event and occurrence available in post_process_group

[wedamija]

Currently, post_process_group is passed a cache key, which is used to fetch the event from eventstore:

sentry/src/sentry/tasks/post_process.py

Lines 332 to 343 in 5d00683

	data = event_processing_store.get(cache_key)
	if not data:
	logger.info(
	"post_process.skipped",
	extra={"cache_key": cache_key, "reason": "missing_cache"},
	)
	return
	with metrics.timer("tasks.post_process.delete_event_cache"):
	event_processing_store.delete_by_key(cache_key)
	event = process_event(data, group_id)

We aren't currently writing this event to eventstore in the issue platform. We have a couple of options here:

• As part of our ingest pipeline, write the event data to eventstore and keep using it as before.
• In post_process_group, when dealing with an issue platform issue, instead of using eventstore we could fetch the event from nodestore. This might make things better for our overall architecture in the future, since we won't have to wait for the slow post_process_group step to complete before we clear the cache.

As well as this, we need to make sure to fetch the occurrence and associate it with the GroupEvent. To do this, we'll need to pass the occurrence id along to post_process_group and load it from nodestore.