How to pass additional data from createOnlineOrder( ) to onOrderPurchased( ) - wix-pricing-plans-backend API

How can I add additional data to the Order object so it can show up when the event is triggered in onOrderPurchased?

I call the createOnlineOrder function to create my Order object. Then I add additional data to the Order object. I call the startPayment function. Once the payment is processed, the onOrderPurchased function is triggered. The Order object is missing the additional data that I need.

When the onOrderPurchased function is triggered, I check the payment status. If the payment status is successful, I will insert data into the collection from the backend since it is more secured than doing so in the frontend. The additional data is needed for the collection.

Front End - I see the testData

		order.testData = testData;
	    console.log(order);
		await wixPayFrontend.startPayment(order.wixPayOrderId);

Backend/event.js - I do not see the testData.

export function wixPricingPlans_onOrderPurchased(event) {
	console.log(event);
}

create order online api - This JSON was copied from the API page so the testData is not shown here. However, I have verified testData is there after I added it.

{
  "order": {
    "id": "5b4fe5c4-67fe-4d67-8239-5c6efc06300b",
    "planId": "5779edd3-2994-4bf4-acfe-d739ad2d95ad",
    "subscriptionId": "281c2e5b-64b2-4acc-adad-58782e1bc40d",
    "wixPayOrderId": "8b4e15a2-4bd8-440d-979d-83d35da5c75a",
    "buyer": {
      "memberId": "805ce40a-9000-464e-85ed-5bb052d8beb7",
      "contactId": "805ce40a-9000-464e-85ed-5bb052d8beb7"
    },
    "pricing": {
      "subscription": {
        "cycleDuration": {
          "count": 1,
          "unit": "MONTH"
        },
        "cycleCount": 0
      },
      "prices": [
        {
          "duration": {
            "cycleFrom": 1
          },
          "price": {
            "subtotal": "15.00",
            "discount": "0",
            "tax": {
              "name": "Tax",
              "rate": "21",
              "amount": "3.15"
            },
            "total": "18.15",
            "currency": "EUR"
          }
        }
      ]
    },
    "type": "ONLINE",
    "status": "DRAFT",
    "autoRenewCanceled": false,
    "lastPaymentStatus": "UNPAID",
    "startDate": "2022-06-02T11:26:04.496420Z",
    "currentCycle": {
      "index": 1,
      "startedDate": "2022-06-02T11:26:04.496420Z",
      "endedDate": "2022-07-02T11:26:04.496420Z"
    },
    "planName": "Gym membership",
    "planDescription": "Get fit fast",
    "planPrice": "15",
    "createdDate": "2022-06-02T11:26:04.496420Z",
    "updatedDate": "2022-06-02T11:26:04.496420Z"
  }
}

on order purchased - This JSON was copied from the API page. This is the JSON that I would get. It is missing testData.

  {
    "metadata": {
      "id":"f2e01b16-48c3-4365-89c7-1e3710639f50",
      "entityId":"938ca26d-41e0-4aae-81a2-286ae9afd6ef",
      "eventTime":"2022-07-26T14:59:49.951623Z",
      "triggeredByAnonymizeRequest":false
    },
    "data": {
      "order": {
        "_id":"938ca26d-41e0-4aae-81a2-286ae9afd6ef",
        "planId":"099e2c86-3b7e-4477-8c27-f77402b8cceb",
        "subscriptionId":"1b879750-b4c3-4b17-9687-1f18f6b0ea19",
        "wixPayOrderId":"3eb01dc8-45c7-426f-a910-13d8c6008532",
        "buyer": {
          "memberId":"ea3d74df-b7dc-4ca1-a7c9-c416b9017a86",
          "contactId":"ea3d74df-b7dc-4ca1-a7c9-c416b9017a86"
        },
        "priceDetails": {
          "subtotal":"74.99",
          "discount":"0",
          "total":"74.99",
          "planPrice":"74.99",
          "currency":"EUR",
          "subscription": {
            "cycleDuration": {
              "count":1,
              "unit":"MONTH"
            },
            "cycleCount":3
          }},
        "pricing": {
          "subscription": {
            "cycleDuration": {
              "count":1,
              "unit":"MONTH"
            },
            "cycleCount":3
          },
          "prices": [{
            "duration": {
              "cycleFrom":1,
              "numberOfCycles":3
            },
            "price": {
              "subtotal":"74.99",
              "discount":"0",
              "total":"74.99",
              "currency":"EUR"
            }
          }]},
        "type":"OFFLINE",
        "orderMethod":"UNKNOWN",
        "status":"ACTIVE",
        "autoRenewCanceled":false,
        "lastPaymentStatus":"PAID",
        "startDate":"2022-01-25T16:23:00.000Z",
        "endDate":"2022-04-25T16:23:00.000Z",
        "pausePeriods":[],
        "earliestEndDate":"2022-04-25T16:23:00.000Z",
        "currentCycle": {
          "index":3,
          "startedDate":"2022-03-25T16:23:00.000Z",
          "endedDate":"2022-04-25T16:23:00.000Z"
        },
        "planName":"Platinum Pro",
        "planDescription":"",
        "planPrice":"74.99",
        "_createdDate":"2022-07-26T14:59:49.314Z",
        "_updatedDate":"2022-07-26T14:59:49.314Z"
      }
    }
  }