MongodbReader cancellation tokens and some unit tests

CoreUnitTests/Infrastructure/Model/TestProjection.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace CoreUnitTests.Infrastructure.Model;
+
+public class TestProjection
+{
+    public Guid TestDocumentId { get; set; }
+
+    public DateTime NestedData { get; set; }
+}