curl --request POST \
  --url https://sandbox.withclasp.com/open_enrollment_windows \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "employer": "<string>",
  "start_date": "2023-12-25",
  "end_date": "2023-12-25",
  "plans": [
    "<string>"
  ],
  "metadata": {}
}
'

{
  "id": "<string>",
  "employer": "<string>",
  "start_date": "2023-12-25",
  "end_date": "2023-12-25",
  "renewal_date": "2023-12-25",
  "completed_at": "2023-11-07T05:31:56Z",
  "completed_member_count": 123,
  "incomplete_member_count": 123,
  "summaries": [
    {}
  ],
  "plans": [
    "<string>"
  ],
  "metadata": {}
}