Prevent approval or payment of invoice with linked order status of "pending"

Purpose: Some libraries want a system block to prevent the approval or payment of invoices when the linked Order has a status of "pending" in order to prevent unwanted encumbrances from accidentally being created when the linked Order is subsequently accessed.

User story statement(s):

As a payer or approver of invoices,
I want to be prevented from paying or approving invoices when the linked Order status is "pending"
so that new encumbrances will not be created when that Order is later accessed

Scenarios:

1. Block approval:
   • Given that an Order associated with a given invoice has a status of "pending"
   • When a staff member attempts to approve the invoice
   • Then the approval should be prevented
2. Block payment:
   • Given that an Order associated with a given invoice has a status of "pending"
   • When a staff member attempts to pay the invoice
   • Then the payment should be prevented
3. Alert user:
   • Given that an Order associated with a given invoice has a status of "pending"
   • When the system prevents approval or payment of that invoice
   • Then the staff member attempting the approval or payment should be alerted that the action was prevented by the system.
     • Message: Invoice can not be approved. One or more of the related orders has a workflow status of "Pending". If desired, please open the related orders before approving this invoice.