Error handling

Errors use one stable envelope:

{"error":{"code":"CUSTOMER_NOT_FOUND","message":"Customer reference was not found","request_id":"00000000-0000-4000-8000-000000000000"}}

Supported codes include INVALID_API_KEY, API_KEY_REVOKED, API_KEY_EXPIRED, INSUFFICIENT_SCOPE, FEATURE_NOT_ENTITLED, ORGANIZATION_NOT_ACTIVE, CUSTOMER_NOT_FOUND, CUSTOMER_ACCESS_DENIED, INVALID_REQUEST, IDEMPOTENCY_KEY_REQUIRED, IDEMPOTENCY_KEY_REUSED, FACTOR_NOT_FOUND, CALCULATION_FAILED, USAGE_LIMIT_REACHED, RATE_LIMITED, and INTERNAL_ERROR. Stack traces, database errors and other internal details are never part of the public response.