The feed opening's request, as the event names it: the request's own ids and reason.
Readonly
The request's request_id: the opening's id.
request_id
The request's reason (cold_start_fetch, following_cold_start, …).
reason
cold_start_fetch
following_cold_start
The request's session_id: the client session it was sent in.
session_id
The feed opening's request, as the event names it: the request's own ids and reason.