**Context**: currently, when trying to move an event page (with registration enabled) to a target outside the Event: namespace, we disallow the page move with the following message: `This event page cannot be moved outside the {{ns:event}} namespace because it has, or had, event registration enabled.`. This was implemented as part of T358704. Now we need to generalize this restriction so that pages with registration enabled cannot be moved to a namespace where event registration is not allowed.
===Acceptance criteria===
When I try to move a page with event registration enabled
AND the target namespace allows event registration
Then the page should be moved.
When I try to move a page with event registration enabled
AND the target namespace **does not** allow event registration
Then the page should **not** be moved
AND I should receive the following error: The event page must be in one of the permitted namespaces.