Full support for System.Text.Json

[qpooqp]

Motivation

In our solution we have need for serialization and deserialization of the models received from delivery client.
The models are generated by model generator.
The models have properties with interface types and the implementation of the interfaces are hidden from us because they are internal to the delivery client library. This causes problem when we want to deserialize them because System.Text.Json can't deserialize to interface without any concrete implementation.

An example can be interface Kontent.Ai.Delivery.Abstractions.IDateTimeContent.

Proposed solution

Expose implementations for the interfaces used in models generated by model generator.

Additional context

I hope that it is understandable what is going on here, but if not, then let me know and i will provide you with some example project.