A handle to an open subscriptions/listen stream. The stream runs on a background task, dispatching the leading notifications/subscriptions/acknowledged and every subsequent opted-in change notification to the client's onNotification (and onProgress). Call cancel() (alias close()) to stop listening; the background task then closes the connection and terminates.
The set of change-notification types a draft client opts into when opening a subscriptions/listen stream (draft basic/utilities/subscriptions). The three list-changed booleans request notifications/tools|prompts|resources/list_changed; resourceSubscriptions lists the resource URIs the client wants notifications/resources/updated for. This is serialised under params.notifications (a SubscriptionFilter) by subscriptionsListen.