curl --request POST \
  --url https://api.useautumn.com/customers/{customer_id}/balances \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "balances": [
    {
      "feature_id": "tokens",
      "balance": 1000
    }
  ]
}'

{
  "success": true
}