feat: add send api method so that entire request message configured

[dennisroche]

Add a Send implementation to IApi.

In my test setup, I have an extension method that builds the HttpRequestMethod using expressions. This removes the hardcoded routes from the tests and compile-time errors when action parameters change.

e.g.

scenario.When
    .Send(r => r.CreateRequest<ValuesController>(c => c.Post(new PostValues { Data = "payload" })));

for

[HttpPost]
public async Task<IActionResult> Post([FromBody] PostValues values)
{
    await Task.CompletedTask;
    return Ok();
}

[sjclark76]

Suggested change

	IResponse Send(Action<HttpRequestMessage> requestSetup);
	IResponse Send(HttpRequestMessage message);

Would that work? it's a bit simpler.