A simple class used to send a "stop" message to an jss::actor instance.
        
namespace jss { class stop_actor {}; }
          #include <jss/actor.hpp>
        
          Calling jss::actor::stop() sends this message to an actor.
          It is the only message type handled automatically by jss::actor::receive().
          If an actor catches exceptions of type jss::stop_actor, it should either rethrow
          the exception or otherwise return from the actor thread function.
        
jss::actor
              class
            jss::actor::stop() member function