Improving the JSON support for the property mediator

[GDLMadushanka]

Description:
Property mediator is used as a "variable" in synapse programming lang.
Currently, it supports the following data types.
STRING, INTEGER, BOOLEAN, DOUBLE, FLOAT, LONG, SHORT, OM
Even though we have OM data type to store XML payloads, we don't have a specific data type to store JSON payloads.
So, currently, we are storing JSON with the string data type and we have to try-parse into JSON to identify whether the payload is a JSON.
This leads to issues like #4924

As improvements, we can introduce a JSON data type to the property mediator.
Also, we can add the json-eval support for such properties as follows.
json-eval($.student.name , ”prop1”)

Suggested Labels:
Improvement

Related Issues:
#5136
json-path/JsonPath#272
#4924