Take a string from the value store, and try to parse it as a JSON. If it succeeds, the resulting JSON will be stored in the value store.
- getGroup: name of the origin key in the sub-store
- getKey: name of the origin sub-store
- resGroup: name of the target sub-store
- resKey: name the value is to be stored as
- On success: The string could be parsed and stored properly
- On fail: The string could not be interpreted as a JSON