curl --request POST \
  --url https://api.loopreturns.com/api/v1/cart/{token} \
  --header 'Content-Type: application/json' \
  --header 'X-Authorization: <api-key>' \
  --data '
{
  "cart": [
    39076568408247
  ]
}
'

{
  "updated": true,
  "data": {
    "cart": [
      39076568408247
    ]
  }
}