[Fix #558] Update event ref (#561)

Signed-off-by: fjtirado <[email protected]>

Author: fjtirado

api/src/main/resources/schema/events/eventref.json

@@ -16,7 +16,8 @@
       "description": "Maximum amount of time (ISO 8601 format) to wait for the result event. If not defined it should default to the actionExecutionTimeout"
     },
     "data": {
-      "type": "string",
+      "type": "object",
+      "existingJavaType": "com.fasterxml.jackson.databind.JsonNode",
       "description": "Expression which selects parts of the states data output to become the data of the produced event."
     },
     "contextAttributes": {