Add new variable mediator

[SanojPunchihewa]

Purpose

Add a new mediator called variable to define variables in the message context.

Synapse configuration

<variable name="string" [action=set/remove] (value="literal" | expression="expression") type="dataType"/>

Default action is set
Allowed data types are: STRING, BOOLEAN, INTEGER, LONG, SHORT, FLOAT, DOUBLE, OM, JSON

Sample XML configs will be as follows,

<variable name="json-array" value="[]" type="JSON"/>
<variable name="var1" expression="json-eval($.result.food)" type="JSON"/>