curl --request POST \
  --url https://app.flowglad.com/api/v1/subscription-item-features \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "subscriptionItemFeature": {
    "subscriptionItemId": "<string>",
    "featureId": "<string>",
    "productFeatureId": "<string>",
    "type": "<string>",
    "amount": null,
    "usageMeterId": null,
    "renewalFrequency": null,
    "expiredAt": 0,
    "detachedAt": 0,
    "detachedReason": "<string>",
    "name": "<string>",
    "slug": "<string>"
  }
}'

{
  "subscriptionItemFeature": {
    "id": "<string>",
    "createdAt": 0,
    "updatedAt": 0,
    "livemode": true,
    "subscriptionItemId": "<string>",
    "featureId": "<string>",
    "productFeatureId": "<string>",
    "type": "<string>",
    "amount": null,
    "usageMeterId": null,
    "renewalFrequency": null,
    "expiredAt": 0,
    "detachedAt": 0,
    "detachedReason": "<string>",
    "name": "<string>",
    "slug": "<string>"
  }
}