Reference
data class Reference(val contextName: String? = null, val aggregateName: String? = null, val contextNameField: String? = null, val aggregateNameField: String? = null) : QuerySemanticType
A value that is the id of an aggregate: the one named by contextName and aggregateName, or, per record, the one named by the sibling string fields contextNameField and aggregateNameField (as a serialized AggregateId holds them). Exactly one of the two pairs is given. Query consumers use it to look up and link to the aggregate; it does not change how the field is queried.