add some default types to de-duplicate similar implmentations

Pilz.Net/Api/Messages/GeneralItemMessages.cs

@@ -0,0 +1,21 @@
+using System.ComponentModel;
+
+namespace Pilz.Net.Api.Messages;
+
+public static class GeneralItemMessages<T>
+{
+    public class Item(T item) : ObjectMessage(item);
+    public class Items(List<T> items) : ObjectsMessage(items);
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public class ObjectMessage(T item) : ApiMessage
+    {
+        public T Item { get; } = item;
+    }
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public class ObjectsMessage(List<T> items) : ApiMessage
+    {
+        public List<T> Items { get; } = items;
+    }
+}