Names a change as the user would recognise it, for the message the Undo and Redo actions show.

The text lives here rather than on the change records: a BibChange is a model value and carries no user-facing text.

A ChangeSet describes itself, because its name is the label of the control the user activated and no derived text can beat that. Everything else is a change recorded on its own, which has no such name, so it is described by what it does.

The switch is exhaustive over the sealed interface: a new kind of change does not compile until it has been given a description here.