curl --request GET \
  --url https://api.leanrails.com/v1/subscription_items/{id} \
  --header 'Authorization: Basic <encoded-value>'

{
  "id": "<string>",
  "object": "subscription_item",
  "subscription": "<string>",
  "price": "<string>",
  "livemode": true,
  "created": 123,
  "quantity": 123
}