List billable metrics

curl --request GET \
  --url https://api.sulu.sh/v0/billableMetrics \
  --header 'Authorization: Bearer <token>'

{
  "object": "list",
  "data": [
    {
      "id": "<string>",
      "object": "billableMetric",
      "name": "<string>",
      "description": "<string>",
      "merchantId": "<string>",
      "unit": "<string>",
      "createdAt": "2023-11-07T05:31:56Z",
      "updatedAt": "2023-11-07T05:31:56Z",
      "aggregation": "SUM",
      "productId": "<string>"
    }
  ],
  "pagination": {
    "limit": 123,
    "offset": 123,
    "total": 123
  }
}