curl --request GET \
  --url https://api.upwell.com/api/rest/customers

{
  "customers": [
    {
      "addresses": [
        {
          "city": "<string>",
          "id": "<string>",
          "stateOrProvince": "<string>",
          "streetLine1": "<string>",
          "streetLine2": "<string>",
          "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"
    }
  ],
  "customersAggregate": {
    "aggregate": {
      "avg": {
        "balance": 123,
        "overdueBalance": 123,
        "overdueInvoiceCount": 123
      },
      "count": 123,
      "sum": {
        "balance": 123,
        "overdueBalance": 123,
        "overdueInvoiceCount": 123
      }
    }
  }
}