Update encumbrance doesn't work as expected

Overview

Upon opening an order, we need to create encumbrances - either all the encumbrances for that order are created, or none of them are. Her we create an order_transaction_summary and accumulate the new encumbrances in temporary_order_transactions.

This behavior is correct, but needs to be expanded upon to accommodate MODINVOICE-113. More specifically:

Upon approving an invoice, we need to update encumbrances via the awaitingPayment API - another all-or-nothing operation. Here we create an invoice_transaction_summary and accumulate the updated encumbrances in temporary_invoice_transactions.

See the wiki for full details.

Acceptance Criteria

• Fix implementation of PUT /finance-storage/transactions/{id} according to the wiki
• Unit tests are updated