Feature Request: Message Filtering

[l-7-l]

RocketMQ's message tags (used for message filtering) are very useful.

For example, an orders topic may contain multiple event types such as OrderCreated and OrderPaid. When a downstream service only depends on one of those events, it can simply subscribe to the corresponding tag.

In Iggy, consumers currently have two choices:

Subscribe to the entire topic and receive all event types, filtering them on the consumer side.
Create a separate topic for each event type.

Both approaches can be wasteful. The former increases unnecessary message traffic and processing overhead, while the latter can lead to topic proliferation and additional operational complexity.

rocketmq concepts: https://rocketmq.apache.org/docs/4.x/producer/01concept1/