How to integrate Slack via Webhooks?

Often, users like to receive alerts in Slack, so they can coordinate on a solution together. The following steps show
how to configure Arthur to send a Webhook to Slack when it finds alerts for a model.

Set up a Slack app
1. Follow the steps in Slack's guide to set up and configure a Slack webhook for a channel: https://api.slack.com/messaging/webhooks
  
  Be sure to note the Webhook URL to add to Arthur next.
Create the webhook in Arthur
Follow the steps in How Do Webhooks Work in Arthur? above to navigate to the webhook creation form. Once there, enter the following information:
1. URL - enter the Slack Webhook URL obtained in step 1
2. Headers - none
3. Body - enter the following JSON, be sure to replace <ARTHUR_URL> with the hostname of your Arthur instance

{
  "text":"Arthur found {{alerts|length}} alerts for model <https://<ARTHUR_URL>/models/{{model.id}}/alerts|{{model.name}}>"
}

Test the webhook
Next, click "TEST WEBHOOK" to attempt to send an example event to the Slack Webhook. Note, this sample will be populated with dummy IDs, so the link will not link to an actual model. When a real alert triggers after saving the webhook, the IDs will be real, so the link will work as expected.