Fetch the briefing data for an interview event. Returns the application,
interview, per-interviewer status, and the feedback form definition id
needed to render an interviewer-facing briefing or to submit feedback via
applicationFeedback.submit.

By default, each interviewer in the response is returned as a userId
with status flags. Pass expand: ["interviewers"] to include the full
user and pool details for each interviewer. Other expansions return the
application, candidate, job, interview, and feedback form definition
inline.

Requires the interviewsRead permission.