Bot for monitoring subscriptions and unsubscriptions in a Telegram channel

The user adds the bot to the channel (as an admin) and this bot notifies the channel owner upon subscription or unsubscription, and it is also possible to view subscription and unsubscription statistics. The user can add only three channels for monitoring (this limit can be changed, for example, by payment). If the bot is not added to the database, then the bot does not respond to subscriptions and unsubscriptions. MySQL database.