code: public AddressTemplate append(String template) {
          String slashTemplate = template.startsWith("/") ? template : "/" + template;
          return AddressTemplate.of(this.template + slashTemplate);
      }
docs: Appends the specified template to this template and returns a new template. If the specified template does
  not start with a slash, "/" is automatically appended.
  
  @param template the template to append (makes no difference whether it starts with "/" or not)
  @return a new template