curl --request GET \
  --url https://api.withflex.com/v1/balance_transactions \
  --header 'Authorization: Bearer <token>'

{
  "balance_transactions": [
    {
      "balance_transaction_id": "<string>",
      "amount": 123,
      "available_on": "<string>",
      "created_at": "<string>",
      "exchange_rate": 123,
      "fee": 123,
      "net": 123,
      "reporting_category": "<string>",
      "checkout_session_id": "<string>",
      "status": "available",
      "source_id": "<string>",
      "type": "<string>",
      "test_mode": true
    }
  ]
}