Support for HttpMessageHandler to allow in-memory web api

[juliencousineau]

Like HttpClient does with

HttpConfiguration config = new HttpConfiguration();

WebApiConfig.Register(config);

_server = new HttpServer(config);

_client = new HttpClient(_server);

It can be really helpful if RestSharp can support like HttpClient!

[shyamgudi]

Any update on this? This would be helpful to have something like this in RestSharp

[alexeyzimarev]

Of course. If you need it - please do it.

[alexeyzimarev]

Duplicate of #747