curl --request GET \
  --url https://api.slash.com/invoice/series \
  --header 'X-API-Key: <api-key>'

{
  "items": [
    {
      "$entity": "invoice_series",
      "id": "<string>",
      "recurrenceRule": {
        "type": "weekly",
        "dayOfWeek": 3
      },
      "paymentTermsDays": 123,
      "invoiceTz": "<string>",
      "startDate": "2023-11-07T05:31:56Z",
      "endCondition": {
        "type": "never"
      },
      "template": {
        "lineItemsAndTotals": {
          "lineItems": [
            {
              "name": "<string>",
              "quantity": 123,
              "priceCents": 123,
              "catalogItemId": "<string>"
            }
          ],
          "discount": {
            "type": "percentage",
            "percent": 123
          },
          "tax": {
            "type": "percentage",
            "percent": 123
          }
        },
        "memo": "<string>",
        "ccEmails": [
          "<string>"
        ]
      },
      "paymentMethods": [
        {
          "method": "ach_debit",
          "config": {
            "passFeeToPayer": true
          }
        }
      ],
      "accountId": "<string>",
      "nextScheduledDate": "2023-11-07T05:31:56Z",
      "legalEntityContactId": "<string>",
      "legalEntityCustomerId": "<string>"
    }
  ],
  "metadata": {
    "nextCursor": "<string>",
    "count": 123
  }
}