How to pass unique id such as customer's id for Square Checkout API?

Nop. I use one time payment function.
This is the request I sent to “/v2/online-checkout/payment-links”.

Then I try to capture payment update webhook to detect if customers made a payment.
The current problem is what I got from “/v2/online-checkout/payment-links” order id is different what I got from webhook payment update’s order id,

-d ‘{
“checkout_options”: {
“allow_tipping”: false,
“ask_for_shipping_address”: false,
“enable_coupon”: false,
“redirect_url”: “https://google.com
},
“description”: “this is sample page”,
“idempotency_key”: “463f7334-f961-4faf-9b77-9d829dbc5066”,
“quick_pay”: {
“location_id”: “LPF38W2R0RWH6”,
“name”: “Purchase date request”,
“price_money”: {
“currency”: “JPY”,
“amount”: 880
}
},
“pre_populated_data”: {
“buyer_email”: “[email protected]”,
“buyer_address”: {
“first_name”: “aaa”,
“last_name”: “bbb”
},
“buyer_phone_number”: “+8108023456789”
}
}’