Add WebProxySettings (use when proxying requests) (#370)

* webproxy part 1

* fixed

* Push to MyGet

* WebProxy standalone

* -n true

* nuget --- "-n true"

* AllowAutoRedirect

* .

src/WireMock.Net/ResponseBuilders/Response.WithProxy.cs

@@ -0,0 +1,48 @@
+using System.Net.Http;
+using WireMock.Http;
+using WireMock.Settings;
+using WireMock.Validation;
+
+namespace WireMock.ResponseBuilders
+{
+    public partial class Response
+    {
+        private HttpClient _httpClientForProxy;
+
+        /// <summary>
+        /// The Proxy URL to use.
+        /// </summary>
+        public string ProxyUrl { get; private set; }
+
+        /// <summary>
+        /// The WebProxy settings.
+        /// </summary>
+        public IWebProxySettings WebProxySettings { get; private set; }
+
+        /// <inheritdoc cref="IProxyResponseBuilder.WithProxy(string, string)"/>
+        public IResponseBuilder WithProxy(string proxyUrl, string clientX509Certificate2ThumbprintOrSubjectName = null)
+        {
+            Check.NotNullOrEmpty(proxyUrl, nameof(proxyUrl));
+
+            var settings = new ProxyAndRecordSettings
+            {
+                Url = proxyUrl,
+                ClientX509Certificate2ThumbprintOrSubjectName = clientX509Certificate2ThumbprintOrSubjectName
+            };
+
+            return WithProxy(settings);
+        }
+
+        /// <inheritdoc cref="IProxyResponseBuilder.WithProxy(IProxyAndRecordSettings)"/>
+        public IResponseBuilder WithProxy(IProxyAndRecordSettings settings)
+        {
+            Check.NotNull(settings, nameof(settings));
+
+            ProxyUrl = settings.Url;
+            WebProxySettings = settings.WebProxySettings;
+
+            _httpClientForProxy = HttpClientHelper.CreateHttpClient(settings);
+            return this;
+        }
+    }
+}