Support RegEx on content target

When creating a page that is served as a child node of some dynamic parent node.
Given a management platform for events, the user may select on one page an event.
When the user navigates to another view, say event-details, this will refer to the previously selected event. If that state is managed via the URL, e.g. /events/123/details, /event/789/detail, etc., this can be targeted with a generic expression in the "targeting" field. Currently it's not supporting such a scenario.