Updating eventshub.go, to ensure receiving custom properties from IoT Hub

Currently, we can receive only the system properties from iot hub. Done changes should allow the retrieval of all custom properties.
It is based on metadata key : requireAllProperties.

By default it is false, if true , looks into the , Properties of Event struct to retrieve the custom properties.

Signed-off-by: mecoding1 <118708378+mecoding1@users.noreply.github.com>

pubsub/azure/eventhubs/eventhubs.go

@@ -73,6 +73,9 @@ const (
 	sysPropIotHubEnqueuedTime         = "iothub-enqueuedtime"
 	sysPropMessageID                  = "message-id"
 
+	// Metadata field to ensure all Event Hub properties pass through
+	requireAllProperties = "requireAllProperties"
+
 	defaultMessageRetentionInDays = 1
 	defaultPartitionCount         = 1
 
@@ -86,7 +89,7 @@ const (
 	maxPartitionCount   = int32(1024)
 )
 
-func subscribeHandler(ctx context.Context, topic string, e *eventhub.Event, handler pubsub.Handler) error {
+func subscribeHandler(ctx context.Context, topic string, getAllProperties bool , e *eventhub.Event, handler pubsub.Handler) error {
 	res := pubsub.NewMessage{Data: e.Data, Topic: topic, Metadata: map[string]string{}}
 	if e.SystemProperties.SequenceNumber != nil {
 		res.Metadata[sysPropSequenceNumber] = strconv.FormatInt(*e.SystemProperties.SequenceNumber, 10)
@@ -124,6 +127,16 @@ func subscribeHandler(ctx context.Context, topic string, e *eventhub.Event, hand
 	if e.ID != "" {
 		res.Metadata[sysPropMessageID] = e.ID
 	}
+	// added properties if any ( includes application properties from iot-hub)
+	if getAllProperties{
+		if e.Properties != nil && len(e.Properties) > 0{
+			for key, value := range e.Properties {
+				if str, ok := value.(string); ok {
+						res.Metadata[key] = str
+				} 
+			}
+		}
+	}
 
 	return handler(ctx, &res)
 }
@@ -626,16 +639,24 @@ func (aeh *AzureEventHubs) Subscribe(subscribeCtx context.Context, req pubsub.Su
 		return err
 	}
 
+	var getAllProperties bool = false
+	if req.Metadata[requireAllProperties] != ""{
+		getAllProperties, err = strconv.ParseBool(req.Metadata[requireAllProperties])
+			if err!=nil{
+					aeh.logger.Errorf("invalid value for metadata : %s . Error: %v.", requireAllProperties, err)
+			}
+	}
+
 	aeh.logger.Debugf("registering handler for topic %s", req.Topic)
 	_, err = processor.RegisterHandler(subscribeCtx,
 		func(_ context.Context, e *eventhub.Event) error {
 			// This component has built-in retries because Event Hubs doesn't support N/ACK for messages
 			b := aeh.backOffConfig.NewBackOffWithContext(subscribeCtx)
-
+			
 			retryerr := retry.NotifyRecover(func() error {
 				aeh.logger.Debugf("Processing EventHubs event %s/%s", req.Topic, e.ID)
-
+				
-				return subscribeHandler(subscribeCtx, req.Topic, e, handler)
+				return subscribeHandler(subscribeCtx, req.Topic, getAllProperties, e, handler)
 			}, b, func(_ error, _ time.Duration) {
 				aeh.logger.Warnf("Error processing EventHubs event: %s/%s. Retrying...", req.Topic, e.ID)
 			}, func() {