curl --request POST \
  --url https://api.maesn.dev/accounting/journalEntries/{journalEntryId}/Attachments \
  --header 'Content-Type: multipart/form-data' \
  --header 'X-ACCOUNT-KEY: <x-account-key>' \
  --header 'X-API-KEY: <x-api-key>' \
  --form file=@example-file

{
  "meta": {
    "warnings": [
      "Field not used by target system"
    ],
    "pagination": {
      "total": 123,
      "perPage": 123,
      "currentPage": 123,
      "totalPages": 123
    }
  },
  "data": [
    {
      "id": "document id",
      "base64Encoded": true,
      "content": "content",
      "contentType": "application/pdf",
      "fileName": "invoice.pdf"
    }
  ]
}