curl --request POST \
  --url https://v2.prod.halliday.xyz/payments/balances \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "payment_id": "pay_abc123",
  "custom_queries": [
    {
      "address": "0xabc1234567890abcdef1234567890abcdef1234",
      "token": "ethereum:0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
    },
    {
      "address": "0xdef1234567890abcdef1234567890abcdef5678",
      "token": "arbitrum:0xfffFFFFFfFFfffFFfFffffFffFFfFFfFFfFFf"
    }
  ]
}
'

{
  "balance_results": [
    {
      "address": "0xabc1234567890abcdef1234567890abcdef1234",
      "token": "ethereum:0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
      "value": {
        "kind": "amount",
        "amount": "<string>",
        "withdrawal_fee": "<string>"
      }
    }
  ]
}