[PP-1] Bubble rejected moves to the user

Overview

In a multi-user environment, one user could set a component as a parent of another, whilst a second user could set the reverse.
At present we get a 400 request if that happens but we should communicate that to the user, restore the state as seen on the server and ask the user to retry their edit.
See https://madebyevan.com/algos/crdt-mutable-tree-hierarchy/

Proposed resolution

Explore that approach

User interface changes