Quick fix for Queue sort by Artist SortName

Fixes #1817

src/Lidarr.Http/REST/RestModule.cs

@@ -20,6 +20,7 @@ namespace Lidarr.Http.REST
         // See src/Lidarr.Api.V1/Queue/QueueModule.cs
         private static readonly HashSet<string> VALID_SORT_KEYS = new HashSet<string>(StringComparer.OrdinalIgnoreCase)
         {
+            "artists.sortname", //Workaround artists table properties not being added on isValidSortKey call
             "timeleft",
             "estimatedCompletionTime",
             "protocol",

src/NzbDrone.Core.Test/Datastore/SortKeyValidationFixture.cs

@@ -17,6 +17,7 @@ namespace NzbDrone.Core.Test.Datastore
             TableMapping.Mapper.IsValidSortKey(sortKey).Should().BeFalse();
         }
 
+        //[TestCase("artists.sortName")] TODO: Figure out why Artists table properties don't get mapped
         [TestCase("Id")]
         [TestCase("id")]
         [TestCase("commands.id")]