Hide obsolete indexer flags from UI

src/Radarr.Api.V3/Indexers/IndexerFlagController.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Mvc;
+using NzbDrone.Common.Extensions;
 using NzbDrone.Core.Parser.Model;
 using Radarr.Http;
 
@@ -13,7 +14,12 @@ namespace Radarr.Api.V3.Indexers
         [HttpGet]
         public List<IndexerFlagResource> GetAll()
         {
-            return Enum.GetValues(typeof(IndexerFlags)).Cast<IndexerFlags>().Select(f => new IndexerFlagResource
+            var type = typeof(IndexerFlags);
+
+            return Enum.GetValues(type)
+                .Cast<IndexerFlags>()
+                .Where(f => type.GetField(f.ToString())?.GetCustomAttributes(false).OfType<ObsoleteAttribute>().Empty() ?? true)
+                .Select(f => new IndexerFlagResource
                 {
                     Id = (int)f,
                     Name = f.ToString()