code: public List<Section> addSections(SoftwareSystem softwareSystem, File directory) throws IOException {
          if (softwareSystem == null) {
              throw new IllegalArgumentException("A software system must be specified.");
          }
  
          return add(softwareSystem, directory);
      }
docs: Adds all files in the specified directory, each in its own section, related to a software system.
  
  @param directory         the directory to scan
  @param softwareSystem    the SoftwareSystem to associate the documentation with
  @return                  a List of Section objects
  @throws IOException      if there is an error reading the files in the directory