Invalidate Parent in Cache on Page Creation

Some use cases employ buttons to create subpages and properties that reference these pages. If on creation the parent page is not invalidated, the user will not see the updated property. This is because the parent page is read from cache and we only recognize changes in exiting pages not on new pages.

Therefore we will invalidate the parent on creation of a page. We may consider later if we can check if the invalidation is really required.