New: (Avistaz Sites) Use created_at_iso for release create date (#2437)

* New: (Avistaz Sites) Use created_at_iso for release create date

no longer have timezone headaches
all Staz sites except animetorrents support this new field.

* fix tests

* Remove AvistaZ TimezoneOffset

src/NzbDrone.Core/Indexers/Definitions/Avistaz/AvistazParserBase.cs

@@ -14,7 +14,6 @@ namespace NzbDrone.Core.Indexers.Definitions.Avistaz
 {
     public class AvistazParserBase : IParseIndexerResponse
     {
-        protected virtual string TimezoneOffset => "-04:00"; // Avistaz does not specify a timezone & returns server time
         private readonly HashSet<string> _hdResolutions = new() { "1080p", "1080i", "720p" };
 
         public Action<IDictionary<string, string>, DateTime?> CookiesUpdater { get; set; }
@@ -66,7 +65,7 @@ namespace NzbDrone.Core.Indexers.Definitions.Avistaz
                     InfoUrl = details,
                     Guid = details,
                     Categories = cats,
-                    PublishDate = DateTime.Parse($"{row.CreatedAt} {TimezoneOffset}", CultureInfo.InvariantCulture, DateTimeStyles.AdjustToUniversal),
+                    PublishDate = DateTime.Parse(row.CreatedAtIso, CultureInfo.InvariantCulture, DateTimeStyles.AdjustToUniversal),
                     Size = row.FileSize,
                     Files = row.FileCount,
                     Grabs = row.Completed,