refs #284

The navigation logic was extensible but also a bit overengineered for
our purposes and kind-of invented a DSL for generating nav entries. We
should be better off with a more direct approach.

Type checks seem to have silently passed even though there were errors
since the upgrade to vue-tsc v2, because the typescript dependency was
too old.

This highlights events with negative durations. There might be other
invalid event states that we could/should visualize so that they are
adressed.

These event states shoud probably be fixed in steering, but it might be
good to spot them if they pop up.

Brightness filter doesn’t look good everywhere.

Timeslots might be cut as a result of conflict solutions. The start and
end time should therefore be part of the cache key.

Up until now the calendar kept a single record of calendar events. This
record was modified whenever new or other events needed to be displayed.
Events were added/changed/removed imperatively (i.e. when
entering/leaving conflict mode), which goes against the principle of
unidirectional data flow embraced by Vue and other reactive frameworks.

The calendar is now split into separate components most importantly the
normal week view and a separate conflict view with separate state
management. The state management itself has been reworked and improved
so that it uses unidirectional data flow.

These changes massively improve performance, simplify state management,
and should make it easier to reason about the code (conflict mode was
hard!).

fixes #287

This is helpful when dealing with iterator objects.

Since we now use a setup component for the calendar the old comments are
no longer relevant and we can use a regular slot.

refs #247

Users have a hard time selecting timeslots if the title column is empty.

refs #274 #276

Steering now creates notes for timeslots automatically.

refs #274 #276

refs #286

Now that bootstrap-vue is no longer used we can finally deactivate the
Vue 2 compatibility mode.