Enum fixes.

src/Squidex/Areas/Api/Controllers/Rules/Models/RuleElementPropertyDto.cs

@@ -6,6 +6,7 @@
 // ==========================================================================
 
 using System.ComponentModel.DataAnnotations;
+using Newtonsoft.Json;
 using Squidex.Domain.Apps.Core.HandleRules;
 
 namespace Squidex.Areas.Api.Controllers.Rules.Models

src/Squidex/Config/Domain/SerializationServices.cs

@@ -25,6 +25,8 @@ namespace Squidex.Config.Domain
     {
         private static JsonSerializerSettings ConfigureJson(JsonSerializerSettings settings, TypeNameHandling typeNameHandling)
         {
+            settings.Converters.Add(new StringEnumConverter());
+
             settings.ContractResolver = new ConverterContractResolver(
                 new AppClientsConverter(),
                 new AppContributorsConverter(),