New Slack integration features

A few evolutions to improve the current Slack integration. Big difference makers: - To not receive a notification every time an Identity receives a message in the Inbox (avoid getting spammed by Slack when you manage many conversations). - To not only mention the LGM identity that received the message, but tag it on Slack. - Add the company name in the Slack notification. Nice to have: - To not show the content of the response. - Get a notification when "goal reached"