Image uploads might take a while and even though we can’t currently show
a progress bar for the upload (because fetch upload progress is still
not a thing) we can at least indicate that something is happening and
disable any interactive UI elements.

refs #144

isProcessing seems more general purpose as it’s not clear if the
provided function actually loads something.

closes #137

refs #127

closes #141

These form components still use bootstrap CSS classes but are part of
our effort to move away from bootstrap.

refs #140

Using :is-open="true" interferes with the dialogs close function in
nested dialogs.

Interfering with the default dialog close logic isn’t that smart because
it handles stuff like nested dialogs for us.

We need to find some other logic to close the dialog when someone clicks
on the backdrop, but that can be a task for a later time.

Using the same name as the native HTML dialog is a bad idea.

refs #89

closes #139

refs #89

We don’t want to show schedules that are in the past because they
clutter the overview.

refs #120

Schedules that only run for a single day should display when that day
is.

refs #121

closes #133

We’ve decided to move the show selector into the navbar because the
selected show is the primary state of the dashboard from which almost
all other state is derived.

Apart from that we now have support for filtering the list based on
active and inactive shows (and possible other criteria in the future) as
it was suggested in #122.

Some iteration semantics got mixed up when replacing remaining uses of
`var` variable declarations in ae37fb6c.

`var foo in bar` cannot be replaced with `const foo of bar` because the
first will assign the iteration index of the current item to foo,
whereas the second will assign the actual iteration item.

This re-implements the auth store with pinia.

Other notable changes:
* the OIDC client configuration and setup is now part of
  separate module that can be included by the OIDC callback routes
  and ensures that we always use the same OIDC client configuration.
* Authorization headers for the steering and tank REST APIs are now
  set with an axios interceptor instead of specifying them for each
  API store action.

refs #127