Customer wants to require a down payment of 30 % for bookings made
one week or more before the actual date, and to make the full payment
otherwise.
This would require yet another relation to keep these values. Fuck it;
i added them to the function, as they are very unlikely to change.
That forced me to change the test for draft_payment to use relative
dates, otherwise there is no way i can have stable results in the
future.
To send the actual mail with sendmail, i have stolen the code from
go-mail[0] and removed everything i did not need. This is because there
is no Go package to send email in Debian 12, and this was easier than
to build the DEB for go-mail.
Once i have the time….
[0]: https://go-mail.dev/