don't persist collab scenes to localStorage

[dwelle]

As a measure to decrease the likelihood that users think they still collaborate on a scene when they open a new tab (or a new tab is opened for them) during collaboration, I'd not persist scene data to localStorage during collaboration so that opening a new tab won't result in the same scene being duplicated (loaded) from localStorage.

During collaboration, we save the data to a server, anyway.

downsides

• when the server is down or the users cannot communicate with it (e.g. their network is down), the scene won't be persisted anywhere. In that case, we can persist to localStorage IFF the saveToFirebase() fails for whatever reason.
• this actually goes against my other proposal: Sync state between tabs on each change

[dwelle]

This also open a question: should we "leak" scene data from collaboration scenes at all?

Case: someone (be it a company or a person) sends you a confidential diagram to collaborate on. You then stop the session (or close the tab etc.). The state when you left the room is kept both in 1) active scene, and 2) localStorage.

This isn't a problem on its own, but may result in expected behavior. For example, you close the tab when collaborating and leave the workstation. Someone then opens a clean excalidraw.com tab and lo and behold, it has the data from your last collaboration.