curl --request POST \
  --url https://api.upwell.com/api/rest/bulk-customers \
  --header 'Content-Type: application/json' \
  --data '
{
  "inputs": [
    {
      "addresses": {},
      "addressesLastUpdatedAt": "2023-11-07T05:31:56Z",
      "billToCustomerId": "<string>",
      "ccEmailAddresses": [
        "<string>"
      ],
      "collectorId": "<string>",
      "contacts": {},
      "contactsLastUpdatedAt": "2023-11-07T05:31:56Z",
      "customerEmailSettings": {},
      "customerIntegrationSettings": {},
      "customerRule": {},
      "deletedAt": "<unknown>",
      "emailAddress": "<string>",
      "metadata": "<unknown>",
      "name": "<string>",
      "paymentLineItems": {},
      "remittanceLineItems": {},
      "sourceSystem": "<string>",
      "sourceSystemId": "<string>"
    }
  ]
}
'

{
  "createCustomers": {
    "returning": [
      {
        "addresses": [
          {
            "city": "<string>",
            "country": "AD",
            "id": "<string>",
            "stateOrProvince": "<string>",
            "streetLine1": "<string>",
            "streetLine2": "<string>",
            "type": "ADDRESS_BOOK",
            "zipOrPostalCode": "<string>"
          }
        ],
        "balance": 123,
        "billToCustomerId": "<string>",
        "ccEmailAddresses": [
          "<string>"
        ],
        "createdAt": "2023-11-07T05:31:56Z",
        "customerRule": {
          "dueOption": 123,
          "id": "<string>"
        },
        "emailAddress": "<string>",
        "id": "<string>",
        "metadata": "<unknown>",
        "name": "<string>",
        "overdueBalance": 123,
        "overdueInvoiceCount": 123,
        "sourceSystem": "<string>",
        "sourceSystemId": "<string>",
        "updatedAt": "2023-11-07T05:31:56Z"
      }
    ]
  }
}