curl --request GET \
  --url https://api.useautumn.com/v1/products/{product_id} \
  --header 'Authorization: Bearer <token>'

{
  "autumn_id": "<string>",
  "created_at": 123,
  "id": "<string>",
  "name": "<string>",
  "env": "production",
  "is_add_on": true,
  "is_default": true,
  "group": "<string>",
  "version": 123,
  "items": [
    {
      "feature_id": "<string>",
      "feature_type": "single_use",
      "included_usage": 123,
      "interval": "<string>",
      "usage_model": "prepaid",
      "price": 123,
      "billing_units": 123,
      "entity_feature_id": "<string>",
      "reset_usage_when_enabled": true,
      "tiers": [
        {
          "to": 123,
          "amount": 123
        }
      ]
    }
  ],
  "free_trial": {
    "duration": "<string>",
    "length": 123,
    "unique_fingerprint": true
  }
}