Get unified billing state

curl --request GET \
  --url https://api.rendobar.com/billing/state

{
  "data": {
    "tier": "<string>",
    "balance": {
      "remainingNd": 123,
      "totalNd": 123,
      "formatted": "<string>"
    },
    "subscription": {
      "planId": "<string>",
      "status": "<string>",
      "periodEnd": 123,
      "cancelAtPeriodEnd": true
    }
  }
}