code: @CheckReturnValue
      public MessageAction clearFiles(Consumer<InputStream> finalizer)
      {
          Checks.notNull(finalizer, "Finalizer");
          for (Iterator<InputStream> it = files.values().iterator(); it.hasNext(); )
          {
              finalizer.accept(it.next());
              it.remove();
          }
          clearResources();
          return this;
      }
docs: Clears all previously added files
  <br>The {@link #clearFiles(BiConsumer)} version provides the resource name for more selective operations.
  
  @param  finalizer
  Consumer useful to <b>close</b> remaining resources,
  the consumer will receive only the resource in the form of an {@code InputStream}
  
  @return Updated MessageAction for chaining convenience
  
  @see    java.io.Closeable