[bug]: System.Object not supported in CRDs

[rgrama]

Describe the bug

Setting a property type to System.Object results in the following error

System.ArgumentException: 'The given type System.Object is not a valid Kubernetes entity.'

I created PR #857 to address this

To reproduce

    [KubernetesEntity(Group = "testing.dev", ApiVersion = "v1", Kind = "TestEntity")]
    private class EntityWithSystemObject : CustomKubernetesEntity<EntityWithSystemObject.EntitySpec>
    {
        public class EntitySpec
        {
            public object Obj { get; set; } = null!;
        }
    }

Expected behavior

System.Object is allowed and XKubernetesPreserveUnknownFields is set automatically

Screenshots

No response

Additional Context

No response

[rgrama]

fixed via #857