curl --request DELETE \
  --url https://api-m.sandbox.paypal.com/v2/invoicing/invoices/{invoice_id}/refunds/{transaction_id} \
  --header 'Authorization: Bearer <token>'

{
  "details": [
    {
      "issue": "<string>",
      "field": "<string>",
      "value": "<string>",
      "location": "body",
      "description": "<string>"
    }
  ],
  "debug_id": "<string>",
  "links": [
    {
      "href": "<string>",
      "rel": "<string>"
    }
  ]
}