[StateMachineBehavior]
public class Document : IStateMachine
{
    public static void Build(IStateMachineBuilder builder) => builder
        .AddInitialState<New>(b => b
            .AddTransition<Review, ApprovalPending>(b => b
                .AddEffect<ReviewEffect>()
            )
            .AddTransition<AfterOneMinute, ReportAutorejection, Rejected>()
        )
        .AddState<ApprovalPending>(b => b
            .AddTransition<Approve, Approved>()
            .AddTransition<Reject, ReportRejection, Rejected>()
        )
        .AddCompositeState<Approved>(b => b
            .AddInitialState<GeneratingInvoice>(b => b
                .AddDoActivity<Invoicing>()
                .AddTransition<DoActivityFinalized, InvoiceGenerated>()
            )
            .AddState<InvoiceGenerated>(b => b
                .AddTransition<PaymentBooked, VerifyPayment, Paid>()
            )
        )
        .AddState<Paid>()
        .AddState<Rejected>()
    ;
}