Display better Slack notifications
Currently, MongoDB Atlas Slack integration only send RAW text.
For easier reading, it would be nice (if not a must have) to leverage Slack notification format to have colors that represent at least the state of an alert.
Here is a suggestion from common things we can see in other tools:
* alert.open: Red
* alert.close: Green
* alert.update: Yellow
* alert.acknowledge: Grey
* alert.cancel: Brown
* alert.inform: Blue
Bonus: Leverage Slack App capabilities and have a
/ command to acknowledge an alert directly from Slack.