Publish and subscribe, alternative modes

[eloylp]

Context

Currently the publish and subscribe system works by sending each message to all available subscribers for a given topic.

Goal

• There are some scenarios in which users would get benefits from a load balancing algorithm, so they can spread the load among the subscribed consumers.
• The change should have a minimal impact in the current API.

[eloylp]

As an idea: Maybe we could think in introducing "options" for the publish command.