Centralize the server config in one place, so it can easily be changed in one
file for all package demos.

This just adds it for the app-shell, for starters.

It got moved to https://gitlab.tugraz.at/dbp/web-components/tugraz-components/-/tree/main/packages/web-components

All apps have been ported to use that package instead.

otherwise it pulls it in from npm

Add another fix to nextcloud. if file is already on the nextcloudserver and the server response while upload with a 403/415 or another error

otherwise we'd have to fix all users

We were using the TU Graz one until now. Instead move
to something that matches DBP somewhat..