public static void serializeStructField(FieldWriter fieldWriter, JsonGenerator generator, FieldBase field, Struct value) {
        DataType dt = value.getDataType();
        if (dt instanceof GeoPosType gpt) {
            if (gpt.renderJsonAsVespa8()) {
                serializeGeoPos(generator, field, value, gpt);
                return;
            }
        }
        serializeStructuredField(fieldWriter, generator, field, value);
    }
@author Steinar Knutsen
@author Vegard Sjonfjell
document/src/main/java/com/yahoo/document/json/JsonSerializationHelper.java