* Initial work on seating
* Add seat guids
* Add product_list_top
* CartAdd: Ignore item when a seat is passed
* Cart display
* product_list_top → render_seating_plan
* Render seating plan in voucher redemption
* Fix failing tests
* Add tests for extending cart positions with seats
* Add subevent_forms to docs
* Update schema, migrations
* Dealing with expired orders
* steps to order change
* Change order positions
* Allow to add seats
* tests for ocm
* Fix things after rebase
* Seating plans API
* Add more tests for cart behaviour
* Widget support
* Adjust widget tests
* Re-enable CSP
* Update schema
* Api: position.seat
* Add guid to word list
* API: (sub)event.seating_plan
* Vali fixes
* Fix api
* Fix reference in test
* Fix test for real
* 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

* Refs #99 -- Fix stripe support for zero-decimal currencies
* Add new money formatting method
* Force decimal places in many places
* Locale-aware currency rendering
* Fix currencies in more places
* More currency fixes
* [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
* little crud
* SubEventItemForm etc
* Drop SubEventItem.active, quota editor
* Fix failing tests
* First frontend stuff
* Addons form stuff
* Quota calculation
* net price display on EventIndex
* Add tests, solve some bugs
* Correct quota selection in more places, consolidate pricing logic
* Fix failing quota tests
* Fix TypeError
* Add tests for checkout
* Fixed a bug in QuotaForm
* Prevent immutable cart if a quota was removed from an item
* Add tests for pricing
* Handle waiting list
* Filter in check-in list
* Fixed import lost in rebase
* Fix waiting list widget
* Voucher management
* Voucher redemption
* Fix broken tests
* Add subevents to OrderChangeManager
* Create a subevent during event creation
* Fix bulk voucher creation
* Introduce subevent.active
* Copy from for subevents
* Show active in list
* ICal download for subevents
* Check start and end of presale
* Failing tests / show cart logic
* Test
* Rebase migrations
* REST API integration of sub-events
* Integrate quota calculation into the traditional quota form
* Make subevent argument to add_position optional
* Log-display foo
* pretixdroid and subevents
* Filter by subevent
* Add more tests
* Some mor tests
* Rebase fixes
* More tests
* Relative dates
* Restrict selection in relative datetime widgets
* Filter subevent list
* Re-label has_subevents
* Rebase fixes, subevents in calendar view
* Performance and caching issues
* Refactor calendar templates
* Permission tests
* Calendar fixes and month selection
* subevent selection
* Rename subevents to dates
* Add tests for calendar views
Scenario 1) Blocking voucher is used in a CartPosition. Previously
too much was subtracted from the quota.
Scenario 2) When two quotas are assigned to a product and one of them
is sold out, blocking vouchers for the other quota should not enable to
buy the product.