Add generator for DateOnly

generator is limited to .net6 and above as it was introduced as part of .net6

src/Atc.Test/Customizations/Generators/DateOnlyGenerator.cs

@@ -0,0 +1,22 @@
+#if NET6_0_OR_GREATER
+namespace Atc.Test.Customizations.Generators;
+
+/// <summary>
+/// Responsible for generating <see cref="DateOnly"/> instances
+/// that has not been canceled.
+/// </summary>
+[AutoRegister]
+public class DateOnlyGenerator : ISpecimenBuilder
+{
+    /// <inheritdoc/>
+    public object Create(object request, ISpecimenContext context)
+    {
+        if (!request.IsRequestFor<DateOnly>())
+        {
+            return new NoSpecimen();
+        }
+
+        return DateOnly.FromDateTime(context.Create<DateTime>());
+    }
+}
+#endif