docs: protected boolean handleAuthHeader(GMS.GmsHeader gms_hdr, AuthHeader auth_hdr, Message msg) {
          if(needsAuthentication(gms_hdr)) {
              if(this.auth_token.authenticate(auth_hdr.getToken(), msg))
                  return true; //  authentication passed, send message up the stack
              else {
                  log.warn("%s: failed to validate AuthHeader (token: %s) from %s; dropping message and sending " +
                             "rejection message",
                           local_addr, auth_token.getClass().getSimpleName(), msg.src());
                  sendRejectionMessage(gms_hdr.getType(), msg.getSrc(), "authentication failed");
                  return false;
              }
          }
          return true;
      }