Added default CTOR to enable deserialization

Author: reshmabidikar

notification/src/main/java/org/killbill/billing/notification/plugin/api/SubscriptionMetadata.java

@@ -28,10 +28,16 @@ public enum ActionType {
         REQUESTED
     };
 
-    private final ActionType actionType;
-    private final String bundleExternalKey;
+    private ActionType actionType;
+    private String bundleExternalKey;
+
+    /**
+     * This is needed for object deserialization.
+     */
+    public SubscriptionMetadata() {
+
+    }
 
-    @JsonCreator
     public SubscriptionMetadata(@JsonProperty("actionType") final ActionType actionType,
                                 @JsonProperty("bundleExternalKey") final String bundleExternalKey) {
         this.actionType = actionType;