fix: delivery timestamp in unix second

Author: alexluong

internal/destregistry/basepublisher.go

@@ -37,7 +37,7 @@ func (p *BasePublisher) StartClose() {
 
 func (p *BasePublisher) MakeMetadata(event *models.Event, timestamp time.Time) map[string]string {
 	systemMetadata := map[string]string{
-		"timestamp": fmt.Sprintf("%d", timestamp.UnixMilli()),
+		"timestamp": fmt.Sprintf("%d", timestamp.Unix()),
 		"event-id":  event.ID,
 		"topic":     event.Topic,
 	}

internal/destregistry/providers/destwebhook/destwebhook.go

@@ -559,7 +559,7 @@ func (p *WebhookPublisher) Format(ctx context.Context, event *models.Event) (*ht
 
 	// Add default headers unless disabled
 	if !p.disableTimestampHeader {
-		req.Header.Set(p.headerPrefix+"timestamp", fmt.Sprintf("%d", now.UnixMilli()))
+		req.Header.Set(p.headerPrefix+"timestamp", fmt.Sprintf("%d", now.Unix()))
 	}
 	if !p.disableEventIDHeader {
 		req.Header.Set(p.headerPrefix+"event-id", event.ID)