OptionalAllowedWhen set, only these agents are offered. Null or omitted offers every agent the user can run.
OptionalPeopleWhen set, these are the people offered, in place of the engine's own user list (which holds only the current user). Null or omitted keeps the engine's list.
Narrows one composer's
@list. The suggestion engine is a process-wide singleton shared by every composer on the page, so anything that differs per chat travels with the request rather than living on the engine; two composers with different scopes never see each other's lists.