def has_role? (*roles, &block)
      user_roles = authorization_engine.roles_for(current_user)
      result = roles.all? do |role|
        user_roles.include?(role)
      end
      yield if result and block_given?
      result
    end
def has_role? (*roles, &block)
      user_roles = authorization_engine.roles_for(current_user)
      result = roles.all? do |role|
        user_roles.include?(role)
      end
      yield if result and block_given?
      result
    end
While permitted_to? is used for authorization, in some cases
 content should only be shown to some users without being concerned
 with authorization.  E.g. to only show the most relevant menu options
 to a certain group of users.  That is what has_role? should be used for.