Use case: A document is shared for editing, but it can have only one editor at a time. When someone request access for edition, a message is broadcasted to all subscribers.

Problem: when someone subscribes later (i.e. after the editor has been designated), that subscriber won’t know who is the editor. How can this subscriber get the last message that was broadcasted, in order to be up-to-date with the state?

More concretely, people join a room, a LiveView, where a document is editable. The document is editable only by one user at the time, there is some checkbox which allows locking/unlocking edition access. When the editor is changing, the new editor is broadcasted.
Problem: If someone joins that room/LiveView later on, he doesn’t know who is editing (and that is really annoying as he thinks no one is editing, and can lock the document for edition while someone was editing).