public Mono<Integer> queryHighestRankByRoleIds(@NotNull Set<Long> roleIds) {
        try {
            Validator.notNull(roleIds, "roleIds");
        } catch (ResponseException e) {
            return Mono.error(e);
        }
        if (roleIds.isEmpty()) {
            return Mono.empty();
        }
        if (roleIds.contains(ADMIN_ROLE_ROOT_ID)) {
            return Mono.just(getRootRole().getRank());
        }
        return adminRoleRepository.findHighestRankByRoleIds(roleIds);
    }
@param adminService is lazy because: AdminService -> AdminRoleService -> AdminService
turms-service/src/main/java/im/turms/service/domain/admin/service/AdminRoleService.java