public void Register(string id, string password)
{
if (Version > 0)
{
throw new InvalidOperationException($"Account with username {id} already exists.");
}
var buddyId = Guid.NewGuid().ToString();
var e = new AccountRegistered(id, password, buddyId);
Publish(e);
}
private void When(AccountRegistered e)
{
Id = e.Id;
}