curl --request POST \
  --url https://api.e-invoice.be/api/validate/ubl \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form file='@example-file'

{
  "id": "<string>",
  "file_name": "<string>",
  "is_valid": true,
  "issues": [
    {
      "message": "<string>",
      "type": "error",
      "schematron": "<string>",
      "location": "<string>",
      "rule_id": "<string>",
      "flag": "<string>",
      "test": "<string>"
    }
  ],
  "ubl_document": "<string>"
}