json.loads(event_data.get("user", {})) crashes with TypeError when
the "user" key is absent because the default value {} is a dict, not
a JSON string. json.loads expects str/bytes, not dict.
Also handle the case where "user" is already a dict (not serialized
JSON) to make the webhook more robust.
Co-authored-by: gambletan <ethanchang32@gmail.com>