Only use asymmetric VKeys for EPP resources (#611)

Given that we currently have no way of reconstituting a symmetric key
from the asymmetric key (or at least, we don't have a 100% reliable way
of doing so) it's best to keep keys as asymmetrical, referring to the
correct database. That way, we don't get situations where we cannot
compare equality of two keys due to one being asymmetrical and one being
symmetrical.

core/src/main/java/google/registry/model/domain/DomainBase.java

@@ -615,7 +615,8 @@ public class DomainBase extends EppResource
 
   @Override
   public VKey<DomainBase> createVKey() {
-    return VKey.create(DomainBase.class, getRepoId(), Key.create(this));
+    // TODO(mmuller): create symmetric keys if we can ever reload both sides.
+    return VKey.createOfy(DomainBase.class, Key.create(this));
   }
 
   /** Predicate to determine if a given {@link DesignatedContact} is the registrant. */