fix #2578 - error notification sent via email includes direct link to specific log item, however redirect was causing an infinite loop. This resolves the problem and also preserves url querystring parameters during login/logout.

Oqtane.Server/Pages/Login.cshtml.cs

@@ -1,3 +1,4 @@
+using System.Net;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Identity;
@@ -43,6 +44,10 @@ namespace Oqtane.Pages
             {
                 returnurl = "";
             }
+            else
+            {
+                returnurl = WebUtility.UrlDecode(returnurl);
+            }
             if (!returnurl.StartsWith("/"))
             {
                 returnurl = "/" + returnurl;