[React Hook] React Hook should emit events on subscription changes

[ewitkon]

When we use React hook to manage the cache we still want to be able to get notified on the changes to the cache, for example, when a new object is added to the cache you might want to present a notification to the user.
One option is to allow for the consumer to register a callback for different events (Add, Delete, Update) and get the updated object, not just the key for the object.