Small refactoring.

src/Squidex.Domain.Apps.Core.Operations/ConvertContent/FieldConverters.cs

@@ -63,7 +63,7 @@ namespace Squidex.Domain.Apps.Core.ConvertContent
             };
         }
 
-        public static FieldConverter ResolveAssetUrls(ISet<string> fields, IAssetUrlGenerator urlGenerator)
+        public static FieldConverter ResolveAssetUrls(IReadOnlyCollection<string> fields, IAssetUrlGenerator urlGenerator)
         {
             if (fields?.Any() != true)
             {

src/Squidex.Domain.Apps.Entities/QueryContext.cs

@@ -28,9 +28,9 @@ namespace Squidex.Domain.Apps.Entities
 
         public bool Unpublished { get; set; }
 
-        public ISet<string> AssetUrlsToResolve { get; private set; }
+        public IReadOnlyCollection<string> AssetUrlsToResolve { get; private set; }
 
-        public ISet<Language> Languages { get; private set; }
+        public IReadOnlyCollection<Language> Languages { get; private set; }
 
         private QueryContext()
         {