Support Slack interactivity webhook

[suhaibmujahid]

This will allow us to act on actions from Slack messages.

[evgenyrp]

I'm curious what you have in mind for this. It can be:

• replying to an existing notification to continue the analysis (probably you meant only this?)
• triggering a new api call with commands
• writing a free-form message that triggers an agent that decides whether to hand over to other agents

[suhaibmujahid]

I'm curious what you have in mind for this.

The first use case will be to trigger the bug-fix agent from the triage notification.