code: @Nonnull
      public Container addContainer(@Nonnull String name, String description, String technology) {
          return getModel().addContainer(this, name, description, technology);
      }
docs: Adds a container with the specified name, description and technology
  
  @param name        the name of the container (e.g. "Web Application")
  @param description a short description/list of responsibilities
  @param technology  the technoogy choice (e.g. "Spring MVC", "Java EE", etc)
  @return the newly created Container instance added to the model (or null)
  @throws IllegalArgumentException     if a container with the same name exists already