Retrieve merchant transaction summary

curl --request GET \
  --url https://staging-vouchers.ventogram.com/api/v1/transactions/summary \
  --header 'X-Api-Key: <api-key>' \
  --header 'X-Api-User: <api-key>'

{
  "success": true,
  "message": "<string>",
  "data": {
    "totalPaid": 123,
    "totalUnpaid": 123,
    "totalRedeemed": 123,
    "totalUnredeemed": 123
  }
}