Update an override shift

curl --request PUT \
  --url https://api.rootly.com/v1/override_shifts/{id} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/vnd.api+json' \
  --data '
{
  "data": {
    "type": "shifts",
    "attributes": {
      "user_id": 123
    }
  }
}
'

{
  "data": {
    "id": "852bf0b1-a6e2-4c5c-9ca1-e6f4735eb0cb",
    "type": "shifts",
    "attributes": {
      "schedule_id": "307c6549-dfb9-48a8-b277-feaf619012cb",
      "rotation_id": "55e256c4-25fc-4eb5-a967-a96c428daa87",
      "user_id": 857,
      "starts_at": "2026-01-29T20:51:19.000-08:00",
      "ends_at": "2026-01-30T04:51:19.000-08:00",
      "is_override": true
    },
    "relationships": {
      "shift_override": {
        "data": {
          "id": "cc45d8a5-3f75-4de1-b403-b327c2cd90cb",
          "type": "shift_overrides"
        }
      },
      "user": {
        "data": {
          "id": "857",
          "type": "users"
        }
      }
    }
  }
}