fix: correctly display total order amount

[willopez]

Resolves #201
Impact: minor
Type: bugfix

Issue

In the orders table, the order total only took into account the amount of the first payment.

Solution

Calculate an order's total by summing all payments

Testing

1. Place an order and split the payment into multiple payments
2. Verify to order total is correctly rendered in the orders table.

[manueldelreal]

Total is now reflected on table rather than just the first payment.

Suggestion implemented

[mikemurray]

👍