Returns activities, newest first. RSVP status history rows have actionable_type MobilizeEventRsvp, actionable_id set to the RSVP id, and a name that starts with rsvp_status:. A status change is named rsvp_status:<from>:<to>:<channel>. A session deletion is named rsvp_status:<status>:session_deleted:<channel>:<start>: the organizer deleted the session, status is the RSVP status at that time, and start is the session start in Unix seconds (empty when the session had no start time). The RSVP status does not change on a session deletion, and the deletion does not count as a missed session. Status tokens are the lowercase RSVP status with every character other than a letter, a digit, or an underscore removed, or none when blank (for example yes, no, maybe, waitlisted, none). Channel tokens are dashboard, api, agent_app, cancel_link, restore_link, confirm_link, ticket_purchase, ticket_refund, host_tools, waitlist, automation, bulk_update, co_host_sync, and unknown. On a history row, assisted_by_id is the user who made the change, or null when no person is known (for example a waitlist promotion). On a MobilizeEventRsvp creation row, assisted_by_id is the agent who created the RSVP; older creation rows have null. A session deletion row carries the deletion time in created_at, but a background job inserts it a few seconds after the deletion, so a sync that uses _since should overlap its window by a few minutes.