curl --request GET \
  --url https://app.flowglad.com/api/v1/invoices/{id} \
  --header 'Authorization: <api-key>'

{
  "invoice": {
    "id": "<string>",
    "createdAt": 0,
    "updatedAt": 0,
    "livemode": true,
    "purchaseId": "<string>",
    "invoiceNumber": "<string>",
    "invoiceDate": 0,
    "billingPeriodId": null,
    "dueDate": 0,
    "customerId": "<string>",
    "organizationId": "<string>",
    "status": "draft",
    "subscriptionId": null,
    "billingRunId": "<string>",
    "billingPeriodStartDate": null,
    "billingPeriodEndDate": null,
    "ownerMembershipId": "<string>",
    "pdfURL": "<string>",
    "receiptPdfURL": "<string>",
    "memo": "<string>",
    "bankPaymentOnly": true,
    "type": "<string>",
    "currency": "USD",
    "taxAmount": -1,
    "subtotal": -1,
    "taxType": "amusement_tax",
    "taxCountry": "AD",
    "taxState": "<string>",
    "taxRatePercentage": "<string>",
    "applicationFee": -1
  },
  "invoiceLineItems": [
    {
      "id": "<string>",
      "createdAt": 0,
      "updatedAt": 0,
      "livemode": true,
      "invoiceId": "<string>",
      "quantity": -1,
      "priceId": "<string>",
      "description": "<string>",
      "price": -1,
      "type": "<string>",
      "ledgerAccountId": null,
      "ledgerAccountCredit": null
    }
  ]
}