* Upgrade Django to 3.0 and other dependencies to recent versions
* Fix otp version contsraint
* Remove six dependency
* Resolve some warnings
* Fix failing tests
* Update django-countries
* Resolve all RemovedInDjango31Warnings in test suite
* Run isort
* Fix import
* Update PostgreSQL version on travis
Negative transactions are never matched automatically, which does not
change. However, when matching them manually, a negative payment was
created, which does not make much sense. Now, if a negative payment is
manually matched, the system checks whether:
a) There is a manual refund in pending state. In this case, the refund
will be marked as done.
b) There is a bank transfer payment of the same amount, in which case
this is handled like a credit card chargeback (i.e. notification on
the dashboard, ...)
c) Otherwise, an error will be returned asking the user to create a
refund object manually.
* Add manual order-matching field for duplicate bankimport transactions
* Only show matching-field for already matched transactions - not for errored ones.
* Upgrade django and stuff
* Update to Django 2.2 and recent versions of similar packages
* Provide explicit orderings to all models used in paginated queries
* Resolve naive datetime warnings in test suite
* Deal with deprecation warnings
* Fix sqlparse version
- [x] Provide data model and configuration toggle
- [x] Allow to delete individual test orders
- [x] Add tests
- [x] Add a prominent warning message to the backend if test mode orders exist (even though test mode is off), as this leads to wrong statistics
- [x] Decide if and how to generate invoices for test orders as invoice numbers cannot be repeated or should not have gaps.
- [x] Decide if and how we expose test orders through the API, since our difference pull mechanism relies on the fact that orders cannot be deleted.
- [x] Decide if and how we want to couple test modes of payment providers?
- [ ] pretix.eu: Ignore test orders for billing
- [ ] Adjust payment providers: Mollie, bitpay, cash, fakepayment, sepadebit
