Add support for `@LinkingObjects`

Similar to Realm Java, we should add support for mapping inverse relationships. The Java annotation of @LinkingObjects seem fine for this.

class Dog : RealmObject { 
  var name: String = "Fido"
  @LinkingObjects("dog")
  val parents: RealmResult<Person> = RealmResults.empty()
}

class Person : RealmObject {
  var name: String = "Jane"
  var dog: Dog? = null
} 

In Java, the LinkingObjects implementation was highly annoying in Kotlin as it wasn’t possible for end users to construct RealmResults themselves which meant that they were forced to do var parents: RealmResults<Person>? = null

We should definitely lift that restriction in the Kotlin SDK. Suggestion would be provide a RealmResults.empty() factory method that basically emulate the empty Results from Core, i.e. it always contains 0 elements. Semantics around queries, adding changelisteners etc. needs to be defined.

[cmelchior]

Hi @ganfra We just started the implementation of this, so hopefully we have something to share soon.

[cmelchior]

Hi @CarsonRedeye . No update yet…it is on our short-term roadmap to implement, but we don’t have any updates right now.