Implement auto-save functionality

Blocked on 🌱 Research: Possible backend implementations of auto-save, drafts, and publishing Active .

I don't know what the scope of this issue was originally intended to be, but I think we have all of it covered in other issues:

• 📌 Autosave PoC Active created a basic implementation.
• 📌 Create AutoSave service and HTTP API to retrieve all entities with pending changes Active improved it.
• ✨ Lazily create draft revisions from valid auto-saved states on demand rather than on save or only on schedule Active is my proposal for how we integrate it with Workspaces. If that proposal is rejected, we'll need to repurpose that issue for an alternate proposal or close that issue and open a new issue with an alternate proposal.