Enable passing in custom JsonSerializerSettings when (de-)serializing to/from JSON

[basdijkstra]

Right now the default settings are used but I can think of plenty of use cases where custom settings might be useful.

Pass in as an overload to Body() for the request and DeserializeTo() and As() for the response.

[basdijkstra]

To test this: create a new test where a request payload containing a date is serialized, use a custom JsonSerializerSettings object with a different value for the DateFormatString property and check that the date is formatted properly in the WireMock stub.

[basdijkstra]

Support for supplying custom JsonSerializerSettings when supplying request body using Body() added in 7db6ca7

Still to do: the same for deserialization, but I need to have a good look at how to create the right overloads.

[basdijkstra]

On second thought: maybe it’s better to pass in these settings in a method of their own rather than using overloads.

Also need to add support for configuring these through RequestSpecification and RestAssuredConfig.

[basdijkstra]

6404657 adds the capability to set custom JsonSerializerSettings for individual tests as well as in a RequestSpecification.

To do: specify custom JsonSerializerSettings to be used when deserializing JSON response payloads.

[basdijkstra]

Added the ability to supply custom JSON deserialization settings using UsingJsonSerializerSettings() when deserializing response bodies from JSON in 2f9c866