creates an override shift

curl --request POST \
  --url https://api.rootly.com/v1/schedules/{schedule_id}/override_shifts \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/vnd.api+json' \
  --data '{
  "data": {
    "type": "shifts",
    "attributes": {
      "starts_at": "2023-11-07T05:31:56Z",
      "ends_at": "2023-11-07T05:31:56Z",
      "user_id": 123
    }
  }
}'

{
  "data": {
    "id": "d4503f41-d583-4142-a2ec-ddf148f48d92",
    "type": "shifts",
    "attributes": {
      "schedule_id": "80e48148-8356-4f2f-8032-3fec60ad7e03",
      "rotation_id": null,
      "starts_at": "2025-09-13T00:29:16.000-07:00",
      "ends_at": "2025-09-13T22:29:16.000-07:00",
      "is_override": true
    },
    "relationships": {
      "shift_override": {
        "data": {
          "id": "dfa51446-5016-476c-b580-3aeb60006f13",
          "type": "shift_overrides"
        }
      },
      "user": {
        "data": {
          "id": "363",
          "type": "users"
        }
      }
    }
  }
}