public Task <Guid?> GetCashier(string username, string password, string cashierName)
{
return(Task.Run <Guid?>(() =>
{
var user = _userRepository.GetUser(username, ComputeSha256Hash(password));
if (user is null)
{
return null;
}
var result = _cashierRepository.GetCashierKey(cashierName);
return result == Guid.Empty ? null : result;
}));
}