curl --request POST \
  --url https://api.kadoa.com/v4/variables/ \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "key": "<string>",
  "value": "<string>",
  "dataType": "STRING"
}
'

{
  "variable": {
    "id": "<string>",
    "key": "<string>",
    "value": "<string>",
    "createdAt": "<string>",
    "dataType": "STRING",
    "updatedAt": "<string>"
  },
  "error": "<string>"
}