Umbrella #25917: Move business logic from Django to middlewared and make websocket API feature complete
Convert Storage:Volumes:Dataset to Middlewared
We need to change legacy UI to create/update/delete datasets using middlewared calls (this is to make sure v1.0 API will continue working as expected)
This is a medium/high risk task, we may introduce new bugs to dataset management.
When this is done we should be able to continue to manage datasets at full extent when using legacy UI.
fix(zfs): Check for mountpoint existence before creating dataset