WithCallback should use also use enum HttpStatusCode (#535)

* Fix #533

* simplyfy code

src/WireMock.Net/Owin/Mappers/OwinResponseMapper.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
+using System.Reflection;
 using System.Text;
 using System.Threading.Tasks;
 using Newtonsoft.Json;
@@ -79,17 +80,22 @@ namespace WireMock.Owin.Mappers
                     break;
             }
 
-            switch (responseMessage.StatusCode)
+            var statusCodeType = responseMessage.StatusCode?.GetType();
+
+            switch (statusCodeType)
             {
-                case int statusCodeAsInteger:
-                    response.StatusCode = MapStatusCode(statusCodeAsInteger);
+                case Type typeAsIntOrEnum when typeAsIntOrEnum == typeof(int) || typeAsIntOrEnum == typeof(int?) || typeAsIntOrEnum.GetTypeInfo().IsEnum:
+                    response.StatusCode = MapStatusCode((int)responseMessage.StatusCode);
                     break;
 
-                case string statusCodeAsString:
+                case Type typeAsString when typeAsString == typeof(string):
                     // Note: this case will also match on null 
-                    int.TryParse(statusCodeAsString, out int result);
+                    int.TryParse(responseMessage.StatusCode as string, out int result);
                     response.StatusCode = MapStatusCode(result);
                     break;
+
+                default:
+                    break;
             }
 
             SetResponseHeaders(responseMessage, response);

test/WireMock.Net.Tests/WireMockServerTests.WithCallback.cs

@@ -0,0 +1,37 @@
+using System.Net;
+using System.Net.Http;
+using System.Threading.Tasks;
+using FluentAssertions;
+using WireMock.RequestBuilders;
+using WireMock.ResponseBuilders;
+using WireMock.Server;
+using Xunit;
+
+namespace WireMock.Net.Tests
+{
+	public partial class WireMockServerTests
+	{
+		[Theory]
+		[InlineData(HttpStatusCode.Conflict)]
+		[InlineData(409)]
+		[InlineData("409")]
+		public async Task WireMockServer_WithCallback_Should_Use_StatusCodeFromResponse(object statusCode)
+		{
+			// Arrange
+			var server = WireMockServer.Start();
+			server.Given(Request.Create().UsingPost().WithPath("/foo"))
+				.RespondWith(Response.Create()
+					.WithCallback(request => new ResponseMessage
+					{
+						StatusCode = statusCode
+					}));
+
+			// Act
+			using var httpClient = new HttpClient();
+			var response = await httpClient.PostAsync("http://localhost:" + server.Ports[0] + "/foo", new StringContent("dummy"));
+
+			// Assert
+			response.StatusCode.Should().Be(409);
+		}
+	}
+}

test/WireMock.Net.Tests/WireMockServerTests.cs

@@ -15,7 +15,7 @@ using Xunit;
 
 namespace WireMock.Net.Tests
 {
-    public class WireMockServerTests
+    public partial class WireMockServerTests
     {
         [Fact]
         public async Task WireMockServer_Should_reset_requestlogs()