This PR adds potentially stale events as available to all addons and
adds a formatted message.
## Discussion
I'd still be interested in hearing input on whether the event type
should be selectable by addons or not before we start emitting the
event. I'm leaning towards "yes", but I'll take your thoughts into
consideration.
https://linear.app/unleash/issue/2-1232/implement-first-iteration-of-the-new-slack-app-addon
This PR implements the first iteration of the new Slack App addon.
Unlike the old Slack addon, this one uses a Slack App (bot) that is
installed to Slack workspaces in order to post messages. This uses
`@slack/web-api`, which internally uses the latest Slack API endpoints
like `postMessage`.
This is currently behind a flag: `slackAppAddon`.
The current flow is that the Unleash Slack App is installed from
whatever source:
- Unleash addons page;
- Direct link;
- https://unleash-slack-app.vercel.app/ (temporary URL);
- Slack App Directory (in the future);
- Etc;
After installed, we resolve the authorization to an `access_token` that
the user can paste into the Unleash Slack App addon configuration form.
https://github.com/Unleash/unleash/assets/14320932/6a6621b9-5b8a-4921-a279-30668be6d46c
Co-authored by: @daveleek
---------
Co-authored-by: David Leek <david@getunleash.io>
