curl --request GET \
  --url https://us.api.flexprice.io/v1/v1/subscriptions/{subscription_id}/schedules

{
  "count": 123,
  "schedules": [
    {
      "can_be_cancelled": true,
      "cancelled_at": "<string>",
      "configuration": {},
      "created_at": "<string>",
      "days_until_execution": 123,
      "error_message": "<string>",
      "executed_at": "<string>",
      "execution_result": {},
      "id": "<string>",
      "metadata": {},
      "schedule_type": "plan_change",
      "scheduled_at": "<string>",
      "status": "pending",
      "subscription_id": "<string>",
      "updated_at": "<string>"
    }
  ]
}