Use client encoding as fallback (restsharp#1693)

Author: alexeyzimarev

src/RestSharp/Response/ResponseHandling.cs

@@ -18,9 +18,9 @@
 namespace RestSharp;
 
 static class ResponseHandling {
-    public static string GetResponseString(this HttpResponseMessage response, byte[] bytes) {
+    public static string GetResponseString(this HttpResponseMessage response, byte[] bytes, Encoding clientEncoding) {
         var encodingString = response.Content.Headers.ContentType?.CharSet;
-        var encoding       = encodingString != null ? TryGetEncoding(encodingString) : Encoding.Default;
+        var encoding       = encodingString != null ? TryGetEncoding(encodingString) : clientEncoding;
         return encoding.GetString(bytes);
 
         Encoding TryGetEncoding(string es) {

src/RestSharp/Response/RestResponse.cs

@@ -14,6 +14,7 @@
 
 using System.Diagnostics;
 using System.Net;
+using System.Text;
 using RestSharp.Extensions;
 
 // ReSharper disable SuggestBaseTypeForParameter
@@ -61,6 +62,7 @@ public class RestResponse : RestResponseBase {
     internal static async Task<RestResponse> FromHttpResponse(
         HttpResponseMessage httpResponse,
         RestRequest         request,
+        Encoding            encoding,
         CookieCollection    cookieCollection,
         CancellationToken   cancellationToken
     ) {
@@ -71,7 +73,7 @@ async Task<RestResponse> GetDefaultResponse() {
             using var stream   = await readTask.ConfigureAwait(false);
 
             var bytes   = stream == null ? null : await stream.ReadAsBytes(cancellationToken).ConfigureAwait(false);
-            var content = bytes == null ? null : httpResponse.GetResponseString(bytes);
+            var content = bytes == null ? null : httpResponse.GetResponseString(bytes, encoding);
 
             return new RestResponse {
                 Content           = content,

src/RestSharp/RestClient.Async.cs

@@ -31,6 +31,7 @@ public async Task<RestResponse> ExecuteAsync(RestRequest request, CancellationTo
             ? await RestResponse.FromHttpResponse(
                     internalResponse.ResponseMessage!,
                     request,
+                    Options.Encoding,
                     CookieContainer.GetCookies(internalResponse.Url),
                     cancellationToken
                 )