MessageThread structure has changed

[fabrizio-turchi]

The class uses the co:element instead of uco-observable:message + "olo:slot".
Example:

{
            "@id": "kb:4237ff8b-e049-4a56-bcf7-e89ed2797d83",
            "@type": "uco-observable:MessageThread",
            "uco-core:hasFacet": [
                {
                    "@id": "kb:0cd2f9f8-9040-4af7-82f8-8287fb3f861d",
                    "@type": "uco-observable:MessageThreadFacet",
                    "identifier": "jane~vivienne@whatsapp.gs.net",
                    "uco-observable:displayName": "Best Friend Chat!!",
                    
                    "uco-observable:messageThread": {
                        "@id": "kb:1a921f84-eadd-4591-be0d-57b936933622",
                        "@type": "uco-types:Thread",
                        "co:size": {
                            "@type": "xsd:nonNegativeInteger",
                            "@value": 2
                        },
                        "co:element": [
                            {
                                "@id": "kb:d8330d5a-b8de-4425-9cd8-a37b038afe81"
                            },
                            {
                                "@id": "kb:3328fbc7-1f63-4e66-b8fc-e27143a64331"
                            }
                        ]                        
                    },
                    
                    "uco-observable:participant": [
                        {
                            "@id": "kb:a5931c7e-fc1e-4def-a618-fc31d9ae4cc7"
                        },
                        {
                            "@id": "kb:f135dee3-ba06-4ded-ad63-5484ce240ec8"
                        }
                    ]
                }
            ]
        }

• co:element refers to a list of Message objects (not ObservableObject!)
• the example uses the class "@type": "uco-observable:MessageThreadFacet", instead of "@type": "uco-observable:ObjectObservable", because it’s a subclass of the latter. Both classes can be used.
• the "co:element" array property is equal to the old uco-observable:message + "olo:slot"
• the "co:item" array property is not compulsory and it serves to indicate the sequential order of the messages (aim not completely clear), the parsers do not use that property
• the "uco-observable:participant" property remains the same
• the items of the co:item link to a message observable but it’s not a uco-observable:ObservableObject but it’s a uco-observable:Message
• the use of "@type": "uco-observable:MessageThread" is because it is a subclass of ObservableObject, so it is also possible uso the super class.