This change implements a show overview page with two display modes:
table and grid. Shows can be ordered and searched. Other filters are not
(yet) implemented.

refs #101
refs #181

The AddShowButton was not rendered when the shows weren’t loaded, but
the only requirement for it to render should be if the user is a
superuser.

This should make the API functions more accessible for callers as there
won’t be any loose undefined values that were sometimes needed to skip
certain values in certain API endpoints.

Instead, every positional argument is now required and all configurable
options or extensions are part of the options object.

refs #179

refs #179

refs #181

Pinia store destructuring doesn’t work on the plain store object. One
has to use storeToRefs or keep the original store object.

see: https://pinia.vuejs.org/core-concepts/

internal note and show owners are both admin-controlled.

refs #146

refs #146

refs #146

The ComboBox is now generic (both in the sense of TypeScript generics as
well as use in other areas as the show selector). It’s behaviour now
also aligns with te TagInput component.

refs #146

refs #121

refs #129

Submitting a note would sometimes fail but user’s were not informed that
something went wrong, because errors not mapped to any form fields were
not displayed.

API object attribute names are now:

1. camelCased (#164)
2. use Id / Ids suffix for object references (#172)

closes #137