public async Task <IActionResult> AddUser([FromForm] ViewModels.ProjectManageUsersViewModel viewModel)
        {
            if (string.IsNullOrEmpty(viewModel.ProjectId))
            {
                return(NotFound());
            }
            if (string.IsNullOrEmpty(viewModel.UserId))
            {
                return(NotFound());
            }
            await _repo.AddUserAsync(new ProjectUser { ProjectId = viewModel.ProjectId, UserId = viewModel.UserId });

            return(RedirectToAction(nameof(ManageUsers), new { id = viewModel.ProjectId }));
        }