Add Listen to subscription events section

Author: angrykoala

modules/ROOT/pages/subscriptions/customize-cdc.adoc

@@ -3,7 +3,7 @@
 :page-aliases: subscriptions/plugins/index.adoc, subscriptions/plugins/amqp.adoc, subscriptions/plugins/single-instance.adoc
 :description: This page describes how to customize the behavior of subscriptions.
 
-GraphQL subscriptions to Neo4j use [Change Data Capture](https://neo4j.com/docs/cdc/current/) (CDC).
+GraphQL subscriptions to Neo4j use link:https://neo4j.com/docs/cdc/current/[Change Data Capture] (CDC).
 Its behavior can be configured by passing an instance of `Neo4jGraphQLSubscriptionsCDCEngine`.
 
 == Neo4jGraphQLSubscriptionsCDCEngine
@@ -44,3 +44,49 @@ const neoSchema = new Neo4jGraphQL({
 });
 ----
 
+== Listen to subscription events
+
+The class `Neo4jGraphQLSubscriptionsCDCEngine` exposes the `events` property, an instance of link:https://nodejs.org/api/events.html#class-eventemitter[EventEmitter], which emits an event for each CDC event. This is useful for scenarios such as forwarding CDC events to an external queue for processing.
+
+[NOTE]
+====
+It is generally recommended to link:https://neo4j.com/docs/cdc/current/[use CDC directly], outside of the GraphQL library, for event listening.
+====
+
+To listen to GraphQL subscription events, use the `.on` method on the `events` property:
+
+[source, javascript, indent=0]
+----
+engine.events.on("create", (payload) => {
+    console.log("Node Created!", payload)
+});
+----
+
+The following CDC-triggered events can be listened to:
+
+* `create`: A node has been created.
+* `update`: A node has been updated.
+* `delete`: A node has been deleted.
+
+=== Event payload
+
+Each event includes a JSON payload with event details:
+
+* `event`: The event type, matching the listener event name.
+* `typename`: The GraphQL type name.
+* `properties`: Contains `old` and `new` objects representing node properties before and after the mutation. These may be `undefined` if the node did not exist before or after the mutation.
+* `id`: The node ID (not exposed through the GraphQL API).
+* `timestamp`: The timestamp of the mutation that triggered the event.
+
+For example, a node creation event would look like this:
+
+[source, javascript, indent=0]
+----
+{
+    event: 'create',
+    typename: 'Movie',
+    properties: { old: undefined, new: { title: 'The Matrix' } },
+    id: '4:70bade62-2121-4808-9348-3ab77859e164:510',
+    timestamp: 1739286926054
+}
+----