As part of the ExESDB.System, the SubscriptionsTracker is responsible for observing the subscriptions that are maintained in the Store.

Since Khepri triggers are executed on the leader node, the SubscriptionsTracker will be instructed to start the Emitters system on the leader node whenever a new subscription is registered.

When a Subscription is deleted, the SubscriptionsTracker will instruct the Emitters system to stop the associated EmitterPool.