def executor(user_account, options = {}) 
      @executor ||= case self.class.name
      when /System/
        then Permit::Executor::System.new self, user_account, options
      else  
        Permit::Executor::Base.new self, user_account, options
      end
    end
def executor(user_account, options = {}) 
      @executor ||= case self.class.name
      when /System/
        then Permit::Executor::System.new self, user_account, options
      else  
        Permit::Executor::Base.new self, user_account, options
      end
    end
return the executor used to execute the permit