16 build core engine

[znas-io]

@aaroneden I've added back the http server functionality to expose the webhook for Slack. I currently use Postman for testing locally so that I can focus on the main functionality. I looked into using the crewAI platform but I'm on the waiting list to get access. In the meantime I resumed working using Langchain and made some progress. Here's a list of some of the changes:

• Added prompt znas/identify_project_status_message
• Added prompt znas/identify_urgent_message
• Added Agent class to encapsulate common agent functionality
• Slack and Jira are now subclasses of Agent
• Using a normal chain (no need for an Agent) to identify urgent vs status_update messages

This is a big PR and I don't like it; I'll assign smaller ones from now on to help with reviewing