MassTransit SagaStateMachine boilerplate from documentation

OrderStateMachine.cs

public record CreateOrder(Guid CorrelationId) : CorrelatedBy<Guid>;

public record ProcessOrder(Guid OrderId, Guid ProcessingId);

public record OrderProcessed(Guid OrderId, Guid ProcessingId);

public record OrderCancelled(Guid OrderId, string Reason);

public class ProcessOrderConsumer : IConsumer<ProcessOrder>
{
    public async Task Consume(ConsumeContext<ProcessOrder> context)
    {
        await context.RespondAsync(new OrderProcessed(context.Message.OrderId, context.Message.ProcessingId));
    }
}

public class OrderState : SagaStateMachineInstance
{
    public Guid CorrelationId { get; set; }
    public string CurrentState { get; set; }
    public Guid? ProcessingId { get; set; }
    public Guid? RequestId { get; set; }
    public Uri ResponseAddress { get; set; }
    public Guid OrderId { get; set; }
}

public class OrderStateMachine : MassTransitStateMachine<OrderState>
{
    public State Created { get; set; }
    
    public State Cancelled { get; set; }
    
    public Event<CreateOrder> OrderSubmitted { get; set; }
    
    public Request<OrderState, ProcessOrder, OrderProcessed> ProcessOrder { get; set; }
    
    public OrderStateMachine()
    {
        InstanceState(m => m.CurrentState);
        Event(() => OrderSubmitted);
        Request(() => ProcessOrder, order => order.ProcessingId, config => { config.Timeout = TimeSpan.Zero; });

        Initially(
            When(OrderSubmitted)
                .Then(context =>
                {
                    context.Saga.CorrelationId = context.Message.CorrelationId;
                    context.Saga.ProcessingId = Guid.NewGuid();

                    context.Saga.OrderId = Guid.NewGuid();

                    context.Saga.RequestId = context.RequestId;
                    context.Saga.ResponseAddress = context.ResponseAddress;
                })
                .Request(ProcessOrder, context => new ProcessOrder(context.Saga.OrderId, context.Saga.ProcessingId!.Value))
                .TransitionTo(ProcessOrder.Pending));
        
        During(ProcessOrder.Pending,
            When(ProcessOrder.Completed)
                .TransitionTo(Created)
                .ThenAsync(async context =>
                {
                    var endpoint = await context.GetSendEndpoint(context.Saga.ResponseAddress);
                    await endpoint.Send(context.Saga, r => r.RequestId = context.Saga.RequestId);
                }),
            When(ProcessOrder.Faulted)
                .TransitionTo(Cancelled)
                .ThenAsync(async context =>
                {
                    var endpoint = await context.GetSendEndpoint(context.Saga.ResponseAddress);
                    await endpoint.Send(new OrderCancelled(context.Saga.OrderId, "Faulted"), r => r.RequestId = context.Saga.RequestId);
                }),
            When(ProcessOrder.TimeoutExpired)
                .TransitionTo(Cancelled)
                .ThenAsync(async context =>
                {
                    var endpoint = await context.GetSendEndpoint(context.Saga.ResponseAddress);
                    await endpoint.Send(new OrderCancelled(context.Saga.OrderId, "Time-out"), r => r.RequestId = context.Saga.RequestId);
                }));
    }
}