Decorate gcp-pubsub stream data

Question

we are using GCP PubSub extensively, using the functional binder approach from spring cloud steam:

        <dependency>
            <groupId>com.google.cloud</groupId>
            <artifactId>spring-cloud-gcp-pubsub-stream-binder</artifactId>
        </dependency>

, and org.springframework.cloud.stream.function.StreamBridge

Is anyone aware of recommended way to intercept such messages? Our use case is we need to manually add a trace identifier to each message. I was looking at using a ChannelInterceptor (e.g. below, which works fine, but not sure if good idea) or an Aspect. Re the Aspect, i have tried a few Point cuts with no joy.

@GlobalChannelInterceptor(patterns = ["[*-out]"])
class OutboundChannelInterceptor : ChannelInterceptor {
    override fun preSend(message: Message<*>, channel: MessageChannel): Message<*> {
        val mutableAccessor = MessageHeaderAccessor.getMutableAccessor(message)
        mutableAccessor.setHeader("aha", System.currentTimeMillis())
        return GenericMessage(message.payload, mutableAccessor.messageHeaders)
    }
}

Any advice much appreciated, thanks