Prod notifications in Slack for CloudBuild activity

TODO: set up a new channel, a webhook, and register the webhook as a secret.

deployment/live/cloudbuild/prod/slack.json

@@ -0,0 +1,30 @@
+[
+    {
+      "type": "section",
+      "text": {
+        "type": "mrkdwn",
+        "text": "Cloud Build {{.Build.ProjectId}} {{.Build.Id}} {{.Build.Status}}"
+      }
+    },
+    {
+      "type": "divider"
+    },
+    {
+      "type": "section",
+      "text": {
+        "type": "mrkdwn",
+        "text": "View Build Logs"
+      },
+      "accessory": {
+        "type": "button",
+        "text": {
+          "type": "plain_text",
+          "text": "Logs"
+        },
+        "value": "click_me_123",
+        "url": "{{.Build.LogUrl}}",
+        "action_id": "button-action"
+      }
+    }
+  ]
+

deployment/live/cloudbuild/prod/terragrunt.hcl

@@ -13,8 +13,9 @@ locals {
 inputs = merge(
   local.common_vars.locals,
   {
-    env               = "prod"
-    cloud_run_service = "distributor-service-ci"
+    env                 = "prod"
+    cloud_run_service   = "distributor-service-ci"
+    slack_template_json = file("slack.json")
   }
 )