curl --request GET \
  --url https://api.paygentic.io/v0/billableMetrics/{id} \
  --header 'Authorization: Bearer <token>'

{
  "id": "bm_u3v4w5x6y7z8a9b0",
  "object": "billableMetric",
  "aggregation": "SUM",
  "createdAt": "2024-02-01T14:45:30Z",
  "description": "Gigabytes of cloud storage utilized",
  "merchantId": "org_c1d2e3f4g5h6i7j8",
  "mode": "usage",
  "name": "Storage Capacity",
  "productId": "prod_k9l0m1n2o3p4q5r6",
  "taxRate": 10,
  "unit": "GB",
  "updatedAt": "2024-02-15T09:20:00Z"
}