private ClientUser ValidateUserLogin(string userName, string password)
{
if (!_storageHandler.UserNameExists(userName))
{
throw new UserNotRegisteredException($"Account with user name '{userName}' is not registered. Please check if you entered correct user name for your account or choose option 'Registration required' to create new account.");
}
ClientUser user = _storageHandler.GetUserByUserName(userName);
if (_storageHandler.ValidatePassword(user, password))
{
return(user);
}
throw new WrongUserPasswordException($"You entered wrong password for account with user name '{userName}'. Please try again.");
}