MERCHANT_ID is the ID assigned by PayPay to identify the merchant.
Please specify the merchant ID displayed on the PayPay for Developers dashboard.
API_KEY and API_SECRET will be the IDs that are numbered to use the API.
Please specify the API key and secret that are displayed on the PayPay for Developers dashboard.
The merchant ID, API key, and secret are different between Test Mode and Live Mode.
Please confirm after selecting Test Mode or Live Mode from the mode switch at the upper right corner of PayPay for Developers.