chore(billing): migrate deprecated slack package to @slack/web-api (#4281)

* chore(billing): migrate deprecated slack package to @slack/web-api

* fix(billing): update node engine to >=18.0.0 for slack web-api compatibility

* refactor: rename web variable to slackClient

Author: angelcaamal

functions/billing/index.js

@@ -23,12 +23,13 @@ const PROJECT_NAME = `projects/${PROJECT_ID}`;
 // [END functions_billing_limit]
 
 // [START functions_billing_slack]
-const slack = require('slack');
+const {WebClient} = require('@slack/web-api');
 
 // TODO(developer) replace these with your own values
 const BOT_ACCESS_TOKEN =
   process.env.BOT_ACCESS_TOKEN || 'xxxx-111111111111-abcdefghidklmnopq';
 const CHANNEL = process.env.SLACK_CHANNEL || 'general';
+const slackClient = new WebClient(BOT_ACCESS_TOKEN);
 
 exports.notifySlack = async pubsubEvent => {
   const pubsubAttrs = pubsubEvent.attributes;
@@ -37,8 +38,7 @@ exports.notifySlack = async pubsubEvent => {
     pubsubAttrs
   )}, ${pubsubData}`;
 
-  await slack.chat.postMessage({
-    token: BOT_ACCESS_TOKEN,
+  await slackClient.chat.postMessage({
     channel: CHANNEL,
     text: budgetNotificationText,
   });

functions/billing/package.json

@@ -5,7 +5,7 @@
   "description": "Examples of integrating Cloud Functions with billing",
   "main": "index.js",
   "engines": {
-    "node": ">=16.0.0"
+    "node": ">=18.0.0"
   },
   "scripts": {
     "compute-test": "c8 mocha -p -j 2 test/periodic.test.js --timeout=600000",
@@ -16,9 +16,9 @@
   "dependencies": {
     "@google-cloud/billing": "^4.0.0",
     "@google-cloud/compute": "^4.0.0",
+    "@slack/web-api": "^7.15.0",
     "google-auth-library": "^9.0.0",
-    "googleapis": "^143.0.0",
-    "slack": "^11.0.1"
+    "googleapis": "^143.0.0"
   },
   "devDependencies": {
     "@google-cloud/functions-framework": "^3.0.0",