Ideally, moving a ticket from one project to another means that the old slug is just the alias for the new one. If that's the case, the link would remain unbrok

Ideally, moving a ticket from one project to another means that the old slug is just the alias for the new one. If that's the case, the link would remain unbroken if the redirection was transparent (ideally with an info message to inform the user that the ticket now has a new slug).