Don't allow to pay for the invoice which was not approved before
In current realization it is possible to pay for the invoice without approval and it leads us to situation, when voucher are not created (voucher are created only on Approval stage).
- Block payment until invoice will be approved
- Clear error should be returned
Add validation in the org.folio.rest.impl.InvoiceHelper#updateInvoice:
1. Check that transition from "Approved" -> "Paid"
2. Check that "approvedBy" and "approvalDate" are filled.
- Logic updated
- Unit test created
- API tests created