Umbrella #25917: Move business logic from Django to middlewared and make websocket API feature complete
Convert Storage:Volume Manager to Middlewared
Ticket to track transfer of business logic from Django/GUI to middlewared and making use of middleware client in GUI.
This is a high risk task, volume creation/extension will be moved from backend and may cause several undesired effects (failure in creation, wrong creation, errors improperly reported, etc)
When this is done we should be able to create volumes of several different topologies, extend existing volumes and get errors on invalid configurations (e.g. trying to extend a raidz volume with a stripe).