Add client IDs for selfservice user in auth credentials (FINERACT-1340)

fineract-provider/src/main/java/org/apache/fineract/portfolio/client/service/ClientReadPlatformService.java

@@ -46,6 +46,15 @@ public interface ClientReadPlatformService {
 
     ClientData retrieveAllNarrations(String clientNarrations);
 
+    /**
+     * Gets a list of Client IDs associated with a user ID.
+     * <p>
+     * This is used in self service authentication
+     *
+     * @param aUserID
+     *            the user id (not null)
+     * @return client IDs listing (may be null)
+     */
     Collection<Long> retrieveUserClients(Long aUserID);
 
     Date retrieveClientTransferProposalDate(Long clientId);