Large sessions support for 1000 attendees (postponed)

Continuous Delivery Collaborate Ultra | Postponed from December release

We're having to postpone the release of this feature that was targeted for December, to address performance concerns in particular use cases. We're working to fix this and release the extension to 1000 users as soon as we can, and will update this release note accordingly. Improvements to the participant list's performance, rolled out in the December release, will remain available for all, but the attendee limit for large sessions will remain at 500 for now.