Slack
Posts a message in the Slack channel you choose for each event. There is no key to copy: you connect on Slack's own screen.
Open Slack in the panel
In Integrations, click Connect on the Slack card. Fill in the Name, tick the events under When to notify and click Connect with Slack.
Pick the channel on Slack
On Slack's screen, check the workspace, pick the channel that will receive the messages and click Allow.
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Slack authorization screen with the channel picker and the Allow button
Run a test
You return to the panel with the Integration connected notice. Click Send test and watch the message arrive in the channel.