docs: document upgrading to 2.0.0 (#160)

* docs: document upgrading to 2.0.0

* docs: add changelog entry

Author: crazyoptimist

CHANGELOG.md

@@ -8,6 +8,7 @@
 * [#155](https://github.com/slack-ruby/slack-ruby-bot-server/pull/155): Enable mongoid to get connection URI from ENV for test - [@crazyoptimist](https://github.com/crazyoptimist).
 * [#157](https://github.com/slack-ruby/slack-ruby-bot-server/pull/157): Added test env setup guide for linux users - [@crazyoptimist](https://github.com/crazyoptimist).
 * [#158](https://github.com/slack-ruby/slack-ruby-bot-server/pull/158): Replace `cursor_pagination` with `pagy_cursor` - [@crazyoptimist](https://github.com/crazyoptimist).
+* [#160](https://github.com/slack-ruby/slack-ruby-bot-server/pull/160): Document upgrading to 2.0.0 - [@crazyoptimist](https://github.com/crazyoptimist).
 * Your contribution here.
 
 #### 1.2.1 (2022/03/06)

UPGRADING.md

@@ -1,6 +1,18 @@
 Upgrading Slack-Ruby-Bot-Server
 ===============================
 
+### Upgrading to >= 2.0.0
+
+#### Replaced Pagination Gem for ActiveRecord
+
+[`cursor_pagination`](https://github.com/Kukunin/cursor_pagination) is abandoned and no longer maintained. It is repaced with [`pagy_cursor`](https://github.com/Uysim/pagy-cursor).
+
+If you're using ActiveRecord, replace `cursor_pagination` with `pagy_cursor` in the Gemfile.
+
+```ruby
+gem 'pagy_cursor'
+```
+
 ### Upgrading to >= 1.2.0
 
 #### New Team Fields