curl --request POST \
  --url https://{host}/schedule/api/employee-assignments \
  --header 'Authorization: <authorization>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "employeeId": 1,
  "workingTimeArrangementId": 1,
  "startsOn": "2023-12-25"
}
'

{
  "workContractId": 1,
  "startsOn": "2023-12-25",
  "employee": {
    "id": 1,
    "firstName": "<string>",
    "lastName": "<string>",
    "displayName": "<string>",
    "jobQualificationName": "<string>",
    "employeeNumber": "<string>",
    "establishmentId": 1,
    "establishmentName": "<string>",
    "department": {
      "id": 1,
      "name": "<string>"
    }
  },
  "id": 1,
  "workingTimeArrangement": {
    "id": 1,
    "name": "<string>",
    "unit": "day"
  },
  "endsOn": "<unknown>"
}