[WIP] Fix #109 -- Waitinglist

[raphaelm]

• Track people who are interested in buying a ticket after the event is sold out
• Notify those users and send them e.g. 24hr-valid blocking vouchers to use
• Manual processing of the list
• Automatic processing of the list
• Variable number of hours validity
• Manual reordering of the list
• Show estimate "You would make an additional XXX € if you increased your quota to fit these people"
• Tests
• Notify admin if capacity is free?
• i18n
• Only allow people to add themselves to the list if waiting list is enabled and product actually sold out

[codecov]

Codecov Report

Merging #405 into master will increase coverage by 0.36%.

@@            Coverage Diff            @@
##           master    #405      +/-   ##
=========================================
+ Coverage   79.24%   79.6%   +0.36%     
=========================================
  Files         157     162       +5     
  Lines       10502   10753     +251     
=========================================
+ Hits         8322    8560     +238     
- Misses       2180    2193      +13

Impacted Files	Coverage Δ
src/pretix/base/settings.py	97.7% <ø> (ø)	✅
src/pretix/control/logdisplay.py	32.07% <ø> (ø)	✅
src/pretix/presale/forms/waitinglist.py	100% <100%> (ø)
src/pretix/base/models/waitinglist.py	100% <100%> (ø)
src/pretix/testutils/settings.py	100% <100%> (ø)	✅
src/pretix/base/models/items.py	96.87% <100%> (+0.14%)	✅
src/pretix/control/forms/event.py	84.57% <100%> (+0.36%)	✅
src/pretix/control/views/item.py	93.54% <100%> (ø)	✅
src/pretix/base/models/init.py	100% <100%> (ø)	✅
src/pretix/control/views/dashboards.py	89% <100%> (+2.25%)	✅
... and 9 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update eb4ba70...714d8bb. Read the comment docs.