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": "3a17a811-937c-441a-a9de-7dc8a2ed8733",
    "type": "shifts",
    "attributes": {
      "schedule_id": "5ee54753-f868-4f71-8fc7-b4e09f522aa8",
      "rotation_id": null,
      "starts_at": "2025-08-22T01:46:26.000-07:00",
      "ends_at": "2025-08-22T23:46:26.000-07:00",
      "is_override": true
    },
    "relationships": {
      "shift_override": {
        "data": {
          "id": "bdf08f9b-14d2-4923-9769-215de7c28745",
          "type": "shift_overrides"
        }
      },
      "user": {
        "data": {
          "id": "347",
          "type": "users"
        }
      }
    }
  }
}