* 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
* Data model + Editor
* Cart and order management
* Rebase migrations
* Fix typos, add tests on cart handling
* Add tests for checkout and quotas
* Add API endpoints
* Validation of settings
* Front page tax display
* Voucher handling
* Widget foo
* Show correct net pricing
* Front page tests
* reverse charge foo
* Allow to require bundling
* Fix test failure on postgres
- [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

- [x] Data model
- [x] display in order view in backend
- [x] review all usages of OrderPositions.objects
- [x] review all usages of order.positions
- [x] review all other model usages
- [x] review plugins
- [x] plugins backwards-compatible API?
- [x] decide on way forward for REST API
- [x] need to cancel fees
- [x] tests
- [ ] plugins
- [ ] gdpr
- [ ] reports
- [x] docs
* Add data shredders for PII
* First working shredder
* Add more shredders
* Add new shredders and download confirmation
* tmp
* PayPal, Stripe, banktransfer
* Add icon to logs
* Untested payment log shredders
* Add waiting list shredder
* First tests
* Add tests for shredders
* Improve templats, link to shredder
* Test payment info shredders
* More tests
* Documentation
* Fix enabled flag in payment provider overview
* Fix minor issues
* Name the default URL
If metrics collection is enabled, the index page of the site will fail
to load: without a name, the metrics middleware throws a TypeError.
* Test for names on all URLs
This test passes if all URLs have names. Without names, URLs will cause
the optional metrics middleware to throw a TypeError.
* check for payment method instead of order total
* incorporate payment fee diff in totaldiff at oder change
* use fee from model and the correct order total
* add error handling
* do not change paid orders
* OrderChangedManager can only be committed once
* remove prints of stripe secrets
* add tests
* an OrderChangeManager must not be committed multiple times
* A pending free order stays pending after being changed
* comments on paid_to_free logic