Can't cancel packed customer shipment
After #11663 (closed), packed shipments can't be cancelled whatsoever because the internal moves are already done.
Before #11663 (closed), as the done-->cancel transition was not allowed, the internal moves would be left dangling, moving stock to the outgoing location. This was very inconvenient but we had our workarounds.
Since this state transition was whitelisted, internal moves are attempted to be canceled on shipment cancel, but a block logic in the write method prevents the state to be modified anyway!
What's the rationale for this changes?