When an Item cannot be satisfied because it is not available, the Buyer has
an option to set it as 'unavailable'.
This is an irreversible action.
The moment the Item is set as unavailable, the new status is recorded and
this is a final status. No further action is possible on the Purchase Request.
Note that this Purchase Request number 152 will now disappear from the
And we no longer see this Item on the list.