556 update id

[LayneHaber]

The Problem

• create updates are not idempotent, and there is a race condition
• The race is between an update initiator completing an update when they don't have priority and an update responder submitting an update at a higher priority (after completing the update from the initiator). If the update initiator is proposing a create update, then it will get re-added into the queue once they receive the message from the responder despite the fact that it syncs from the responder's proposed update.

The Solution

• Adds update.id, making the create updates idempotent
• Adds store migrations to make sure the update is retrievable by id
• Checks on start of queue if an update has already been executed