{
  "type": "object",
  "properties": {
    "eventType": { "type": "string", "enum": ["SHIFT_STARTED", "SHIFT_ENDED"] },
    "lineId": { "type": "string" },
    "shiftName": { "type": "string" },
    "shiftTarget": { "type": "integer" },
    "timestamp": { "type": "integer", "format": "int64" }
  },
  "required": ["eventType", "lineId", "shiftName", "shiftTarget", "timestamp"]
}