public Flux<Long> findBlockedUserIds(@NotNull Long groupId, @NotNull Set<Long> userIds) {
        try {
            Validator.notNull(groupId, "groupId");
            Validator.notNull(userIds, "userIds");
        } catch (ResponseException e) {
            return Flux.error(e);
        }
        List<GroupBlockedUser.Key> keys = new ArrayList<>(userIds.size());
        for (Long userId : userIds) {
            keys.add(new GroupBlockedUser.Key(groupId, userId));
        }
        return groupBlocklistRepository.findIdsByIds(keys)
                .map(user -> user.getKey()
                        .getUserId());
    }
@return whether the user to unblock was blocked
turms-service/src/main/java/im/turms/service/domain/group/service/GroupBlocklistService.java