New invoicing format (for the following patrons) (Patreon)

I have now switched to a subscription-based charging format, where a patreon is charged based on the day of the month they joined, not the 1st. For example, if you subscribe on the 25th of this month, you will be charged the following month on the 25th of next month.

The format for those who paid on the 1st of the month remains the same, they will
be charged on the 1st of the following month.

- Greetings, KiimmoTK.