Behavior: Returns the list of users associated with a live channel, organized into two groups: Items contains currently online users with active sessions, and RelatedItems contains offline shared-access users (with " (offline)" suffix on LastName) and users with pending invitations. Currently only supports live channel content definitions — other content types return an empty result. The authenticated user is always included in the online results.

Authorization: Requires a valid Bearer token (class-level [Authorize]).

Side Effects: None.

Error Scenarios: Returns an empty result if the id does not match a supported live channel content definition. Returns 404 if the session data cannot be retrieved.