* Add JSON type definitions
* Sample use
* Keep mutable for a follo-up PR (avoid dead code)
* Use list/dict
* Remove JsonObjectType
* Remove reference to Union
* Cleanup
* Improve rest
* Rename json_dict => json_data
* Add docstring
* Add type hint to json_loads
* Add cast
* Move type alias to json helpers
* Cleanup
* Create and use json_loads_object
* Make error more explicit and add tests
* Use JsonObjectType in conversation
* Remove quotes