private async Task <string> GenerateRefreshToken(Guid memberId, DateTime?expires = null) { string refreshToken = RandomStringGenerator.Generate(64); if (expires == null) { expires = DateTime.UtcNow.AddDays(_settings.RefreshTokenLifetimeDays); } MemberRefreshToken token = new MemberRefreshToken(Guid.Empty, memberId, expires.Value, refreshToken); await _memberRepository.AddRefreshToken(token); return(refreshToken); }