4788: Ability to configure which messages are sent to Slack

avanthong

What version are you running?

3.0.8

What's the URL of the page this enhancement relates to, if any?

http://reviewboard/admin/integrations/rbintegrations.slack.integration.SlackIntegration/configs/add/

Describe the enhancement and the motivation for it.

The "Add webhooks" admin page provides a very useful feature where the admin can select which events get sent to the webhook - the options are: "All events", "Review request closed", "Review request published", "Review request reopened", "Review published", and "Reply published".
When configuring Slack integration, this option is not provided, and "all events" are sent to the Slack webhook.
Would it be possible to have this same feature from "Add webhook" to be added to the Slack integration?

What operating system are you using? What browser?

Server is hosted on Linux. Client is Linux. Browser is Firefox 57

Please provide any additional information below.

Missing feature aside, love the new Slack integration added in 3.0!