curl --request GET \
  --url https://api.unprice.dev/v1/invoices/{invoiceId} \
  --header 'Authorization: Bearer <token>'

{
  "invoice": {
    "id": "<string>",
    "project_id": "<string>",
    "subscription_id": "<string>",
    "customer_id": "<string>",
    "status": "unpaid",
    "currency": "USD",
    "statement_key": "<string>",
    "statement_start_at": 123,
    "statement_end_at": 123,
    "due_at": 123,
    "past_due_at": 123,
    "issue_date": 123,
    "sent_at": 123,
    "paid_at": 123,
    "total_amount": 1
  },
  "lines": [
    {
      "entry_id": "<string>",
      "statement_key": "<string>",
      "kind": "<string>",
      "description": "<string>",
      "quantity": 123,
      "amount": 1,
      "currency": "USD",
      "created_at": "2023-11-07T05:31:56Z"
    }
  ]
}