private async Task UpdateUserAsync(InvitationDO invitation)
        {
            var user = await _userRepository.GetUserByIdAsync(invitation.UserId);

            if (user != null)
            {
                if (user.GroupIDs is null)
                {
                    user.GroupIDs = new List <string>();
                }
                user.GroupIDs.Add(invitation.GroupId);
                await _userRepository.UpdateUserAsync(user);
            }
        }
 public async Task AddInvitationAsync(InvitationDO invitation)
 {
     await _context.Invitations.InsertOneAsync(invitation);
 }