Configurable JSON DE-serialization support (Newtonsoft.Json vs System.Text.Json)

[Stepami]

Is your feature request related to a problem? Please describe.

Currently, i am unable to control how WireMockServer accepts incoming messages. I would like to have API for request builders similar to what we got after #1341

Describe the solution you'd like

IJsonConverter jsonConverter = new MyJsonConverter();

Request.Create().WithBody(new MyDto(), jsonConverter);
Request.Create().WithBodyAsJson(new MyDto(), jsonConverter);
Request.Create().WithBodyAsProtoBuf(
    "greeter.GreetRequestGrpc",
    new JsonMatcher(new GreetRequestGrpc(), jsonConverter));

[StefH]

@Stepami

My solution for this is to create a new SystemTextJsonMatcher which can be used.
Because most methods support passing a IMatcher already.

---

#1447

[Stepami]

Well, as those interfaces are public, my guess is I could do it myself