Specify exact data format for all numeric fields

Confirming REJECTED transactions leads to HTTP 5xx

Handle customer product deactivations gracefully

Validate country codes

Validate callback URLs

Subservices for products under the Gift Cards service

Allow UUID and ULID formats for purchaser_id

Response validation failures due to bad payment product data

Launch product subservices, Support additional_identifier fields

Error code 1009503 (HTTP 503) to denote system maintenance