fix issue action executed after compensation triggered

[cikupin]

Re-PR this issue. Need review by maintainer.

What I fixed

• Order & payment logic still executed even though compensatePurchaseItem had been executed. This means order & payment logic shouldn't be executed.

saga.AddSubTxDef(labelPurchaseItem, purchaseItemFailed, compensatePurchaseItem).
    AddSubTxDef(labelOrder, orderSuccess, compensateOrder).
    AddSubTxDef(labelPayment, paymentSuccess, compensatePayment)

ctx := context.Background()
property := &orderProperty{}
saga.StartSaga(ctx, sagaTopicID).
    ExecSub(labelPurchaseItem, property, input.Item).
    ExecSub(labelOrder, property, input.Item, input.Price).
    ExecSub(labelPayment, property, input.PaymentMethod, input.Price).
    EndSaga()

• Add IsAborted() function to detect whether saga is complete or aborted.

Example:

sagaInstance := saga.StartSaga(ctx, sagaTopicID).
    ExecSub(labelPurchaseItem, property, input.Item).
    ExecSub(labelOrder, property, input.Item, input.Price).
    ExecSub(labelPayment, property, input.PaymentMethod, input.Price).
    EndSaga()

if sagaInstance.IsAborted() {
    // do something if saga is aborted
}

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This change is