Fix open api.

backend/src/Squidex/Areas/Api/Config/OpenApi/OpenApiServices.cs

@@ -103,6 +103,8 @@ namespace Squidex.Areas.Api.Config.OpenApi
         {
             settings.AllowReferencesWithProperties = true;
 
+            settings.ReflectionService = new ReflectionServices();
+
             settings.TypeMappers = new List<ITypeMapper>
             {
                 CreateStringMap<DomainId>(),

backend/src/Squidex/Areas/Api/Config/OpenApi/ReflectionServices.cs

@@ -0,0 +1,38 @@
+// ==========================================================================
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex UG (haftungsbeschraenkt)
+//  All rights reserved. Licensed under the MIT license.
+// ==========================================================================
+
+using Namotion.Reflection;
+using NJsonSchema.Generation;
+using Squidex.Infrastructure.Collections;
+
+namespace Squidex.Areas.Api.Config.OpenApi
+{
+    public class ReflectionServices : DefaultReflectionService
+    {
+        protected override bool IsArrayType(ContextualType contextualType)
+        {
+            if (contextualType.Type.IsGenericType &&
+                contextualType.Type.GetGenericTypeDefinition() == typeof(ImmutableList<>))
+            {
+                return true;
+            }
+
+            return base.IsArrayType(contextualType);
+        }
+
+        protected override bool IsDictionaryType(ContextualType contextualType)
+        {
+            if (contextualType.Type.IsGenericType &&
+                contextualType.Type.GetGenericTypeDefinition() == typeof(ImmutableDictionary<,>))
+            {
+                return true;
+            }
+
+            return base.IsDictionaryType(contextualType);
+        }
+    }
+}