Create end user transactions (async)

curl --request POST \
  --url https://app.herondata.io/api/end_users/{end_user_id_or_heron_id}/transactions \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '{
  "balances": [
    {
      "account_id": "checking_account_202348",
      "batch_closing_balance": 25000.45
    }
  ],
  "transactions": [
    {
      "account_id": "checking_account_202348",
      "amount": -42.42,
      "balance": 423,
      "categories_default": "shopping",
      "currency": "USD",
      "date": "2020-04-27",
      "description": "GOOGLE *ADS12340929 [email protected] US",
      "mcc_code": "<string>",
      "order": 123,
      "reference_id": "my_favourite_transaction_231098",
      "timestamp": "2021-11-12T10:38:05Z",
      "transaction_code": "card"
    }
  ]
}'

{
  "request_id": "<string>",
  "transactions_loaded": 123
}