Fixes CA input preselection and adds conditional rendering

[marwyg]

Fixes the errors from the last merge: opencast#979

Also adds the typical "red star" next to the field name to mark the field as mandatory. The field will now only be rendered, when a "location" has inputs.

[github-actions]

Use docker or podman to test this pull request locally.

Run test server using develop.opencast.org as backend:

podman run --rm -it -p 127.0.0.1:3000:3000 ghcr.io/arnei/opencast-admin-interface:pr-9

Specify a different backend like stable.opencast.org:

podman run --rm -it -p 127.0.0.1:3000:3000 -e PROXY_TARGET=https://stable.opencast.org ghcr.io/arnei/opencast-admin-interface:pr-9

It may take a few seconds for the interface to spin up.
It will then be available at http://127.0.0.1:3000.
For more options you can pass on to the proxy, take a look at the README.md.

[marwyg]

I had a type bug in it. It's fixed now.

[marwyg]

I also noticed that, after the creation of a new scheduled event, when you want to change the channels in the event details it wouldn't work properly. I will force push changes to fix the schedule configuration tab in the event details.

[github-actions]

This pull request has conflicts ☹
Please resolve those so we can review the pull request.
Thanks.