As a follow-on story to
MODFISTO-28, budget.awaitingPayment should never be less than 0. When a credit is processed, awaitingPayment should decreases as described on the wiki, but never below 0.
awaitingPayment: 10, and you receive a credit of 20, awaitingPayment -> 0.
The wiki has been updated/clarified with the necessary calculation details.
- budget.awaitingPayment is updated upon credit as described on the wiki
- unit tests are updated