Add new property to model to simply access planned durations of AK

Add contact email address to event model
Show email link in footer
Fix missing event reference in AKDetailView

The subfolder is not under version control, however, you can place another version controlled source here if needed

prevent jetbrains IDE from omitting this import

associate AKTrack with an Event
associate AKCategory with an Event
restrict AK requirements to those associated with the same event
restrict AK categories to those associated with the same event

truncate before numbering
remove debug print statements

add default slot size to Event model
set initial form value to event deafult slot size

if ': ' cut off starting there
if ' - ' cut off starting there
if ' (' cut off starting there
cut to appropriate length

Only change appearance of owner field for normal submission but not for wishes (since they don't have owners)

Submission form

See merge request kif/akplanning!4

Add base url field to event
Generate Wiki link from title and base url

Improve blank and unique constraints of model:
- allow blank starting times of slotes to store durations before scheduling and adapt string representation
- change unique constraint from name and shortname of AK to unique for each event only
Implement handling of tags for submission and update (auto-creation) by using a semicolon-separated text file instead of multiple choice field
Implement handling of durations for submission
Automatically generate short name
Use different forms for submission and update
Use special adapted template for AK updates instead of submission template
Fix EventSlugMixin for POST requests

Set URLs for edit views in templates

Add choosen-js library and assets for nicer looking multiple select
Add new blocks for loading of individual assets to base template
Use choosen-js for multiple fields in AK submission view

Introduce existing owner select field and dispatching views for POST submitted owner id
Adapt redirection flows
Adapt submission overview template
Introduce Owner edit view
Fix prepopulation issue in AKWish creation view (caused by inheritance)
Adapt template name to role as create and update template
Fix context issue for AK creation view (missing owner attribute)