conforming-agent: Add Schema Validation to Xml/JsonProvider

## Description / As-Is

XML/JsonProvider convert any incoming message/request body into java structures. By knowing the execution environment, an attacker could try to design input structures in order to target the evaluation logic behind.

## How it should be

XML/JsonProvider should validate incoming message/request bodies according to a set of allowed schemas. this restricts the opportunities to design arbitrary input structures.