Moving an event to a different calendar should also make it a sub page of that calendar

It is possible to select a different calendar via drop down when editing an event, either in the dialog version or the full edit view.
Doing so moved the new event to the new calendar in the old, deprecated "parent-child" hierarchy, but it does not move the event as a subpage into the new calendar.

The event is shown in the new calendar anyway, but it is not the expected behaviour with nested pages.

When moving an event, name collision with already existing events (or other pages) need to be taken into account.