Some client may want a unique invoice billing time from several project.
We can achieve that by allowing the user to select an invoice wich can be completed on the screen https://localhost:8443/projectmgr/control/projectBilling?projectId=9000 .
To keep integrity, this invoice needs to be :
- at status INVOICE_IN_PROGRESS
- the party to bill must be the same for the two project
This is a first step to enable billing Scrum project an Project on the same invoice.