Add otherClientId to HistoryEntry

This CL adds an otherClientId field to be populated on domain transfers with client ID of the other end of the transaction (losing registrar for requests and cancels, gaining registrar for approves and rejects). This will be used for reporting in compliance with specification 3 of the ICANN registry agreement.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=143775945

java/google/registry/flows/domain/DomainTransferRequestFlow.java

@@ -211,6 +211,7 @@ public final class DomainTransferRequestFlow implements TransactionalFlow {
   private HistoryEntry buildHistory(Period period, DomainResource existingResource, DateTime now) {
     return historyBuilder
         .setType(HistoryEntry.Type.DOMAIN_TRANSFER_REQUEST)
+        .setOtherClientId(existingResource.getCurrentSponsorClientId())
         .setPeriod(period)
         .setModificationTime(now)
         .setParent(Key.create(existingResource))