@Override
    public String visit(SystemStreamPartition systemStreamPartition, StartpointUpcoming startpointUpcoming) {
      return EventHubSystemConsumer.END_OF_STREAM;
    }
Offers a eventhub specific implementation of {@link StartpointVisitor} that resolves
different types of {@link Startpoint} to samza offset.
samza-azure/src/main/java/org/apache/samza/system/eventhub/admin/EventHubSystemAdmin.java