Ensure uninherited types are sealed

Resolved mediator source geenrator conflict with tests

LiteCharms.Features/CancellationTokenProvider.cs

@@ -0,0 +1,16 @@
+namespace LiteCharms.Features;
+
+public sealed class CancellationTokenProvider : IDisposable
+{
+    private readonly CancellationTokenSource source = new();
+
+    public CancellationToken Token => source.Token;
+
+    public void Dispose()
+    {
+        source.Cancel();
+        source.Dispose();
+
+        GC.SuppressFinalize(this);
+    }
+}