Update LogisticsEvents model to latest cargo ontology

The current implementation of the LogisticsEvent model expects to be eventCode property of type xsd#string However, according to the latest cargo onoloty, https://onerecord.iata.org/ns/cargo#eventCode property is of type https://onerecord.iata.org/ns/cargo#CodeListElement

Example:

POST ../logistics-events

{
    "@context": {
        "@vocab": "https://onerecord.iata.org/ns/cargo#"
    },
    "@type": "LogisticsEvent",
    "@id": "https://1r.example.com/logistics-object/abcd/logistics-events/xyz",
    "eventTimeType": {
        "@id": "https://onerecord.iata.org/ns/cargo#ACTUAL"
    },
    "eventCode": {
        "@id": "https://onerecord.iata.org/ns/coreCodeLists#StatusCode_ARR"
    },
    "eventDate": {
        "@type": "http://www.w3.org/2001/XMLSchema#dateTime",
        "@value": "2023-04-01T14:38:01.000Z"
    },
    "recordedAtLocation": {
        "@id": "https://1r.example.com/logistics-objects/JFK"
    }
}

GET https://1r.example.com/logistics-object/abcd/logistics-events/xyz

{
    "@context": {
        "@vocab": "https://onerecord.iata.org/ns/cargo#"
    },
    "@type": "LogisticsEvent",
    "@id": "https://1r.example.com/logistics-object/abcd/logistics-events/xyz",
    "eventTimeType": {
        "@id": "https://onerecord.iata.org/ns/cargo#ACTUAL"
    },
    "eventCode": "https://onerecord.iata.org/ns/coreCodeLists#StatusCode_ARR",
    "eventDate": {
        "@type": "http://www.w3.org/2001/XMLSchema#dateTime",
        "@value": "2023-04-01T14:38:01.000Z"
    },
    "recordedAtLocation": {
        "@id": "https://1r.example.com/logistics-objects/JFK"
    }
}