Device actual state not visible during device deletion

The device deletion process may take a long time. During that period of time the device states remain as ENABLED/ACTIVE/REACHABLE. Therefore, if an operator queries a device while it's being deleted the device state will be misleading.

There are two possible solution to the problem:

• Add "deleting" to the device reason (we are already using the reason field for transient messages like omci-flows-deleted"). The reason field is visible on device queries. Since the device reason is a text field and not formalized then it may be tricky for an operator to act on it.
• Augment the operational state of the device to include all device operational transient states - e.g. deleting, deleting-failed, disabling, disabling-failed).

I think option 2 is a better option as it provides a clear state of the device and potentially could allow NB requests for specific device states (may be a delete request of a disabling-failed device vs a disabled device would need different actions)