This app uses legacy RTM client and custom bot

Should migrate to a [modern Slack app](https://api.slack.com/docs/apps) and [Bolt](https://github.com/slackapi/bolt-js).

No new apps can be created, but existing ones will continue to work for now. From the [Slack changelog](https://api.slack.com/changelog#entry-september_2024_2):
> * Beginning **March 31, 2025**, we will discontinue support for legacy custom bots. For your integrations to continue working, you must create brand new [Slack apps](https://api.slack.com/docs/apps).
> * In **March 2026**, we will discontinue support for classic apps. For your apps to continue working, you will need to [migrate them to Slack apps](https://api.slack.com/authentication/migration).