enabler: propose a generic interface for response post-processors

[mhordynski]

Feature description

• allow to attach a generic postprocessor for the agent responses
  • it should be able to modify, reject or accept response
  • it can also rerun the agent with modified input
• how to support streaming? probably it can run chunk by chunk, or perform some grouping
• interface should clarify how it support (or not) streaming

Motivation

Make supervisor feature using a generic interface.

Additional context

No response