Send a follow-up E-Mail if a trial expired for a user and no payment was made

[bohdan-shulha]

We need to understand why our users churn, so these follow-up e-mails may help to understand what stops them from using the service.

Detect if the user had cancelled the subscription before sending. If they've cancelled - send a follow up, if they didn't cancel but payment failed - create a next ticket. :D