Struct:
{
    "initiator": {
        "type": "EXTERNAL_USER",
        "userInfo": {
            "uid": "cc30f81a052d28c34cb775ac24",
            "user_name": "chia",
            "cn": {
            "ru": "Алиса",
        "en": "Alyssa"
        },
            "orgId": [23, 75]
        }
    },
    "id": "ea8af463-a692-4890-9835-cc67a69e51d9",
    "class": {
        "id": "someId",
        "class", "CLASS"
    }
}

schema.xml fields:
initiator.type
initiator.userInfo.uid
initiator.userInfo.user_name
initiator.userInfo.cn.en
initiator.userInfo.cn.ru
initiator.userInfo.orgId
id
ip_address
msg.id
msg.text

Spring Data Solr Entity:
@SolrDocument(collection = "test")
public class Message {

    @Id
    @Indexed
    private String id;

    @?
    private Map<String, Object> initiator;

    @JsonProperty("class")
    private Clazz clazz;