curl --request GET \
  --url https://api.polygon.technology/v0.9/customers/{id}/balance \
  --header 'Authorization: Bearer <token>'

{
  "data": {
    "customerId": "<string>",
    "estimatedBalanceCurrencyCode": "<string>",
    "estimatedBalanceValue": "<string>",
    "updatedAt": "2023-11-07T05:31:56Z"
  }
}