In requests, `wf_params` were handled as a string (JSON encoded), while in responses, they were treated as a `Dict[str, Any]`.
This worked fine as long as `wf_params` were consistently in JSON format.
However, depending on the workflow engine, `wf_params` may not always adhere to the JSON format.
This update addresses that issue and ensures compatibility across different workflow engines.
**Full Changelog**: https://github.com/sapporo-wes/sapporo-service/compare/2.0.2...2.0.3