added migration guide for v3

.github/workflows/ci-build.yml

@@ -16,7 +16,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 14.x]
+        node-version: [12.x, 14.x, 15.x]
 
     steps:
     - uses: actions/checkout@v2

docs/_tutorials/migration_v3.md

@@ -0,0 +1,117 @@
+---
+title: Migrating to V3
+order: 2
+slug: migration-v3
+lang: en
+layout: tutorial
+permalink: /tutorial/migration-v3
+---
+# Migrating to v3.x
+
+<div class="section-content">
+This guide will walk you through the process of updating your app from using `@slack/bolt@2.x` to `@slack/bolt@3.x`. There are a few changes you'll need to make but for most apps, these changes can be applied in 5 - 15 minutes.
+
+*Note: Make sure to checkout our [support schedule](#slackbolt1x-support-schedule) for `@slack/bolt@2.x` if you don't plan on upgrading right away*
+</div> 
+
+---
+
+### Org Wide App Installation Changes to InstallationStore & orgAuthorize
+
+In [Bolt for JavaScript 2.5.0](https://github.com/slackapi/bolt-js/releases/tag/%40slack%2Fbolt%402.5.0), we introduced support for [org wide app installations](https://api.slack.com/enterprise/apps). To add support to your applications, two new methods were introduced to the Installation Store used during OAuth, `fetchOrgInstallation` & `storeOrgInstallation`. With `@slack/bolt@3.x`, we have dropped support for these two new methods for a simpler interface and to be better aligned with Bolt for Python and Bolt for Java. See the code samples below for the recommended changes to migrate.
+
+Before:
+
+```javascript
+installationStore: {
+    storeInstallation: async (installation) => {
+      // change the line below so it saves to your database
+      return await database.set(installation.team.id, installation);
+    },
+    fetchInstallation: async (InstallQuery) => {
+      // change the line below so it fetches from your database
+      return await database.get(InstallQuery.teamId);
+    },
+    storeOrgInstallation: async (installation) => {
+      // include this method if you want your app to support org wide installations
+      // change the line below so it saves to your database
+      return await database.set(installation.enterprise.id, installation);
+    },
+    fetchOrgInstallation: async (InstallQuery) => {
+      // include this method if you want your app to support org wide installations
+      // change the line below so it fetches from your database
+      return await database.get(InstallQuery.enterpriseId);
+    },
+  },
+```
+
+After:
+
+```javascript
+installationStore: {
+    storeInstallation: async (installation) => {
+      if (installation.isEnterpriseInstall) {
+        // support for org wide app installation
+        return await database.set(installation.enterprise.id, installation);
+      } else {
+        // single team app installation
+        return await database.set(installation.team.id, installation);
+      }
+      throw new Error('Failed saving installation data to installationStore');
+    },
+    fetchInstallation: async (InstallQuery) => {
+      // replace database.get so it fetches from your database
+      if (InstallQuery.isEnterpriseInstall && InstallQuery.enterpriseId !== undefined) {
+        // org wide app installation lookup
+        return await database.get(InstallQuery.enterpriseId);
+      }
+      if (InstallQuery.teamId !== undefined) {
+        // single team app installation lookup
+        return await database.get(InstallQuery.teamId);
+      }
+      throw new Error('Failed fetching installation');
+    },
+  },
+```
+
+Along with this change, we have also dropped support for `orgAuthorize`, and instead recommend developers to use `authorize` for both the single workspace installs and org wide app installs (if you are not using the built-in OAuth or providing a token when initializing App). See the code sample below for migration steps:
+
+Before:
+
+```javascript
+const app = new App({ authorize: authorizeFn, orgAuthorize: orgAuthorizeFn, signingSecret: process.env.SLACK_SIGNING_SECRET });
+
+const authorizeFn = async ({ teamId, enterpriseId}) => { 
+  // Use teamId to fetch installation details from database
+}
+
+const orgAuthorizeFn = async ({ teamId, enterpriseId }) => { 
+  // Use enterpriseId to fetch installation details from database
+}
+```
+
+After:
+```javascript
+const app = new App({ authorize: authorizeFn, signingSecret: process.env.SLACK_SIGNING_SECRET });
+
+const authorizeFn = async ({ teamId, enterpriseId, isEnterpriseInstall}) => { 
+  // if isEnterpriseInstall is true, use enterpriseId to fetch installation details from database
+  // else, use teamId to fetch installation details from database
+}
+```
+
+### HTTP Receiver as default
+
+In `@slack/bolt@3.x`, we have introduced a new default [`HTTPReceiver`](https://github.com/slackapi/bolt-js/issues/670) which replaces the previous default `ExpressReceiver`. This will allow Bolt for JavaScript apps to easily work with other popular web frameworks (Hapi.js, Koa, etc). `ExpressReceiver` is still being shipped with Bolt for JavaScript and `HTTPReceiver` will not provide all the same functionality. One use case that isn't supported by `HTTPReceiver` is creating custom routes (ex: create a route to do a health check). For these use cases, we recommend continuing to use `ExpressReceiver` by importing the class, and creating your own instance of it, and passing this instance into the constructor of `App`. See [our documentation on adding custom http routes](https://slack.dev/bolt-js/concepts#custom-routes) for an example.
+
+### @slack/bolt@2.x support schedule
+
+`@slack/bolt@2.x` will be deprecated on **January 12th, 2020**. We will only implement **critical bug fixes** until the official end of life date and close non critical issues and pull requests, which is slated for **May 31st, 2021**. At this time, development will fully stop for `@slack/bolt@2.x` and all remaining open issues and pull requests will be closed. 
+
+### Minimum Node Version
+
+`@slack/bolt@3.x` requires a minimum Node version of `12.13.0` and minimum npm version of `6.12.0` .
+
+### Minimum TypeScript Version
+
+As outlined in our [using TypeScript guide](https://slack.dev/bolt/tutorial/using-typescript), `@slack/bolt@3.x` requires a minimum TypeScript version of `4.1`.

package.json

@@ -22,7 +22,7 @@
   ],
   "engines": {
     "node": ">=12.13.0",
-    "npm": ">=6.4.1"
+    "npm": ">=6.12.0"
   },
   "scripts": {
     "prepare": "npm run build",