Rule formatter registered.

src/Squidex/Config/Domain/ReadServices.cs

@@ -89,6 +89,9 @@ namespace Squidex.Config.Domain
             services.AddSingletonAs<AppProvider>()
                 .As<IAppProvider>();
 
+            services.AddSingletonAs<RuleEventFormatter>()
+                .AsSelf();
+
             services.AddSingletonAs<ContentChangedTriggerHandler>()
                 .As<IRuleTriggerHandler>();