The purchase_progress section of the response to get-basket-price and add-basket now includes an array of objects -
one for each active wallet or progress campaign. Each object contains general wallet or progress campaign information, the previous and new balance for the
customer, and an array of individual mutations. This allows API clients to build a full picture for inclusion in e.g. receipts.
The response to get-basket-price and add-basket now includes a voucher_created section describing vouchers which
may have (provisionally) been created as a result of a transaction.
