Retrieve a credit grant 

{
  "id": "credgr_test_61R9a6NUWsRmOW3RM41L6nFOS1ekDGHo",
  "object": "billing.credit_grant",
  "amount": {
    "monetary": {
      "currency": "usd",
      "value": 1000
    },
    "type": "monetary"
  },
  "applicability_config": {
    "scope": {
      "price_type": "metered"
    }
  },
  "category": "paid",
  "created": 1726620803,
  "customer": "cus_QrvQguzkIK8zTj",
  "effective_at": 1729297860,
  "expires_at": null,
  "livemode": false,
  "metadata": {},
  "name": "Purchased Credits",
  "priority": 50,
  "test_clock": null,
  "updated": 1726620803
}