SLING-9389: Distribution Event Properties enhanced for holding queue item creation time stamp (#7)

Co-authored-by: chiki <chiki@adobe.com>
diff --git a/src/main/java/org/apache/sling/distribution/event/DistributionEventProperties.java b/src/main/java/org/apache/sling/distribution/event/DistributionEventProperties.java
index 3a13b55..555ee3f 100644
--- a/src/main/java/org/apache/sling/distribution/event/DistributionEventProperties.java
+++ b/src/main/java/org/apache/sling/distribution/event/DistributionEventProperties.java
@@ -56,4 +56,9 @@
      * Package id
      */
     String DISTRIBUTION_PACKAGE_ID = "distribution.package.id";
+
+    /**
+     * property containing the time when an item was created and enqueued for distribution
+     */
+    String DISTRIBUTION_ENQUEUE_TIMESTAMP = "distribution.enqueue.timestamp";
 }