- [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

* Custom HTML email renderers
* Move inline_css call
* Small fixes
* New HTML mail style for pretix
* Thumbs
* Inlinestyle for notifications
* Documentation
* Set line-height
* 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
* [WIP] add date/time question type
* Date/time questions python classes, types and form handling
* use own timepicker
* Fix argument naming
* Add css and js for datetimepickers
* remove not needed str call
* seperate splitdatetime widget template and fix date/time questions
* change date placeholder to dec 31
* do not show seconds in presale time pickers
* improve codestyle
* add new question types to api doc
* add test
* expand test to datetime question
* add new questiontypes to changelog
remove duplicate parens
* remove timezone from time only question answers
* improve codestyle
* Fix date and time formatting in control question overview
* Data model and migration
* Some backwards compatibility
* CRUD for checkin lists
* Show and perform checkins
* Correct numbers in table and dashboard widget
* event creation and cloning
* Allow to link specific exports and pass options per query
* Play with the CSV export
* PDF export
* Collapse exports by default
* Improve PDF exporter
* Addon stuff
* Subevent stuff, pretixdroid tests
* pretixdroid tests
* Add CRUD API
* Test compatibility
* Fix test
* DB-independent sorting behavior
* Add CRUD and coyp tests
* Re-enable pretixdroid plugin
* pretixdroid config
* Tests & fixes