OpenAPiExample - adds support for data and serialized value

[baywet]

OAI 3.2.0 defined two new fields for OpenAPI example

• dataValue (JsonNode?)
• serializedvalue (string?)

We should add fields for to the model, and support for serialization/deserialization.

In 3.1.0 these fields should be serialized with an x-oai- prefix, making them extensions.