Placeholders in subject were not being replaced because there was
no `.format()` called on the subject.
This commit creates a context dict that is used for both the body
and the subject. It is then replaced using `.format_map()`
Fixes https://github.com/pretix/pretix/issues/531
* New concept for fee handling
* More usages
* Remove all usages, make all tests pass
* API changes
* Small fixes
* Fix order of invoice lines
* Rebase migration
* added fields and logic for adding quota in creation of product
* added section for selecting quota option
* logic for hiding quota selections when needed
* fixed logic for quota selection
* formatting, removed print statements
* styling
* tests for adding quotas in product form
* cleaned up
* added divs
* reworked to include translatable text, readable values for quota options
* quota_add_existing form assignment to str(q.pk)
* made changes for radio buttons, added in sliding animation
* moved string constants for quota options, changed quota options to RadioSelect from Select
* Addition of all basics required for microdata
Microdata for event added to the head of the base event html template.
* Fixed flake8 errors & included settings checks
Fixed the flake8 too many blank line errors and changed the date and time section to refer to settings before including the time and/or the date_to.
* Typo in last commit
Fixed typo in last commit
* Fixed bracket mistake and flake8 error
Fixed tab between { and % in template tag. Removed extra lines. Removed unnecessary str() call.
Corrected binary & to [and] operator.
* Added testing for microdata
Testing added to the presale.test_event tests to cover the 4 branches and basic microdata functionality.
* 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
