Fix /api/clients API broken by #12

openid-connect-common/src/main/java/org/mitre/oauth2/model/ClientDetailsEntity.java

@@ -155,7 +155,7 @@ public class ClientDetailsEntity implements ClientDetails {
   private Date createdAt; // time the client was created
   private boolean clearAccessTokensOnRefresh = true; // do we clear access tokens on refresh?
   private Integer deviceCodeValiditySeconds; // timeout for device codes
-  private ClientLastUsedEntity clientLastUsed; // last used info
+  private transient ClientLastUsedEntity clientLastUsed; // last used info
   private boolean active = true;
   private Date statusChangedOn;
   private String statusChangedBy;