Migrate data for new conversation schema

import io.realm.DynamicRealm

import io.realm.FieldAttribute

import io.realm.RealmMigration

import io.realm.Sort

class QkRealmMigration : RealmMigration {

                    ?.removeField("read")

                    ?.removeField("me")

            val conversations = realm.where("Conversation")

                    .findAll()

            val messages = realm.where("Message")

                    .sort("date", Sort.DESCENDING)

                    .distinct("threadId")

                    .findAll()

                    .associateBy { message -> message.getLong("threadId") }

            conversations.forEach { conversation ->

                conversation.setObject("lastMessage", messages[conversation.getLong("id")])

            }

            version++

        }