code: public ConnectionHandler<R, W> end(ConnectionHandler<RR, WW> handler) {
          return interceptor.intercept(handler);
      }
docs: Terminates this chain with the passed {@link ConnectionHandler} and returns a {@link ConnectionHandler} to be
  used by a {@link TcpServer}
  
  @param handler Connection handler to use.
  
  @return A connection handler that wires the interceptor chain, to be used with {@link TcpServer} instead of
  directly using the passed {@code handler}