@Override
    public List<UserSessionsInfo> getSessions(Set<Long> userIds) {
        List<UserSessionsInfo> sessions = new ArrayList<>(userIds.size());
        for (Long userId : userIds) {
            sessions.add(getUserSessions(userId));
        }
        return sessions;
    }
@return closed session count
@implNote The method will be called definitely when a session is closed no matter it is
          closed by the client or the server, and the method will clean up sessions in both
          local and Redis.
turms-gateway/src/main/java/im/turms/gateway/domain/session/service/SessionService.java