Make http status code available

[kabaluk]

Issue #1468

Made HttpStatusCode available for ease of testing.

Common Usage scenario:
Testing if you got the right Status result from a function returning IHttpResult.
Currently no easy way of checking the actual result.
Exposing the HttpStatusCode solves the below scenario.

public class Functions
{
    [LambdaFunction]
    [HttpApi(LambdaHttpMethod.Get, "/resource/{type}")]
    public IHttpResult GetResponse(string type, ILambdaContext context)
    {
        return type == "good" ?
            HttpResults.Ok() :
            HttpResults.BadRequest();
    }
}

public class HtttpResultsStatusCodeUsage
{
    [Fact]
    public void UsageOfIHttpResultStatusCode()
    {
        var sut = new Functions();

        var result = sut.GetResponse("good", null);

        Assert.Equal(HttpStatusCode.OK, result.StatusCode);

        result = sut.GetResponse("not good", null);

        Assert.Equal(HttpStatusCode.BadRequest, result.StatusCode);
    }
}

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[normj]

Looks good!

[ashovlin]

Thanks! "Source Generator CI" is expected to fail because this is from a fork, but not concerned.

[chrispaynter]

Nice!

[normj]

Version 0.13.3 is out with this PR. Thanks again for the PR!