Configure Slack Bot permissions and get an API token.
Send transactional messages from your app to Slack.

Episode source code:
https://github.com/corsego/93-slack-api/commit/deec85cc1e9940dbcec4f6a03da42e34fce5458d
Gem slack-ruby-client:
https://github.com/slack-ruby/slack-ruby-client
Text version of this video:
https://blog.corsego.com/slack-api-with-rails
Slack API:
https://api.slack.com