curl --request POST \
  --url https://api.skinshark.gg/merchant/users \
  --header 'Content-Type: application/json' \
  --header 'api-key: <api-key>' \
  --data '
{
  "email": "jsmith@example.com",
  "steamId": "<string>",
  "externalId": "<string>"
}
'

{
  "requestId": "<string>",
  "success": true,
  "data": {
    "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "email": "<string>",
    "steamId": "<string>",
    "externalId": "<string>",
    "feeBps": 123,
    "createdAt": "2023-11-07T05:31:56Z",
    "idempotent": true
  },
  "error": {
    "code": 1500,
    "key": "INSUFFICIENT_BALANCE",
    "message": "Insufficient balance"
  }
}