Fix the payout consumer that skips repeat deliveries

An assistant's SQS consumer credited a payout every time a message arrived. SQS standard queues deliver at least once, so a message can come back after a timeout or a crash, and the account gets paid twice. The fix keeps a record of the payout ids already applied.

An assistant wrote apply_payouts(account_ids, starting_balances, deliveries). It is in the editor. It has a bug. Find it and fix it.

Input and output:

• account_ids: the account ids, as strings.
• starting_balances: integers, the same length as account_ids. Each is the balance of the account at the same position.
• deliveries: the messages in the order they arrive, each meant to be "payout_id|account_id|amount". The same message can arrive more than once.
• Return the final balances, in the order of account_ids.

Rules the tests check:

• Skip a delivery that does not split on | into exactly 3 parts.
• Skip it when the payout id is empty, or when that payout id has already been applied.
• Skip it when the account id is not in account_ids. If an id appears more than once there, use the first one.
• Skip it unless the amount is 1 to 12 characters, every one a digit from 0 to 9, and its value is above 0. Leading zeros are fine.
• Otherwise add the amount to that account's balance, and record the payout id as applied.
• A skipped delivery records nothing, so a later delivery with the same payout id can still be applied.