Create separate cookie web client

Web/CookieWebClient.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Net;
+
+#pragma warning disable SYSLIB0014 // 'WebClient.WebClient()' is obsolete
+namespace SabreTools.RedumpLib.Web
+{
+    public class CookieWebClient : WebClient
+    {
+        // https://stackoverflow.com/questions/1777221/using-cookiecontainer-with-webclient-class
+        private readonly CookieContainer _container = new();
+
+        /// <summary>
+        /// Get the last downloaded filename, if possible
+        /// </summary>
+        public string? GetLastFilename()
+        {
+            // If the response headers are null or empty
+            if (ResponseHeaders == null || ResponseHeaders.Count == 0)
+                return null;
+
+            // If we don't have the response header we care about
+            string? headerValue = ResponseHeaders.Get("Content-Disposition");
+            if (string.IsNullOrEmpty(headerValue))
+                return null;
+
+            // Extract the filename from the value
+            return headerValue.Substring(headerValue.IndexOf("filename=") + 9).Replace("\"", "");
+        }
+
+        /// <inheritdoc/>
+        protected override WebRequest GetWebRequest(Uri address)
+        {
+            WebRequest request = base.GetWebRequest(address);
+            if (request is HttpWebRequest webRequest)
+                webRequest.CookieContainer = _container;
+
+            return request;
+        }
+    }
+}