Fix the AddBody issue with byte[] value #1761

Author: alexeyzimarev

src/RestSharp/Request/RestRequestExtensions.cs

@@ -313,7 +313,7 @@ public static RestRequest AddBody(this RestRequest request, object obj, string?
 
         return
             obj is string str            ? request.AddParameter(new BodyParameter("", str, contentType)) :
-            obj is byte[] bytes          ? request.AddParameter(new BodyParameter("", bytes, contentType)) :
+            obj is byte[] bytes          ? request.AddParameter(new BodyParameter("", bytes, contentType, DataFormat.Binary)) :
             contentType.Contains("xml")  ? request.AddXmlBody(obj, contentType) :
             contentType.Contains("json") ? request.AddJsonBody(obj, contentType) :
                                            throw new ArgumentException("Non-string body found with unsupported content type", nameof(obj));