/// <summary>
/// Gets the user identifier by email address.
/// </summary>
/// <param name="emailAddress">The email address.</param>
/// <returns></returns>
public Optional <int> GetUserIdByUserName(string emailAddress)
{
if (emailAddress.IsEmpty())
{
throw new ArgumentException("Got empty email address");
}
return(CustomerQueries.GetUserIdByUserName(emailAddress));
}
