Fix "invalid scale configuration" error and more

[Arnei]

Fixes #282.

The statistics page (and statistics tab in the event and series details) is currently broken. The web console shows the error "Invalid scale configuration for scale: XAxes".

This fixes the error and a few less critical bugs to get the statistics page up and running again.

Unfortunately, testing this is not straightforward. To thoroughly test this, you would need an Opencast with a statistics provider set up and configured, which is more difficult than it sounds. The interested may check the docs: https://docs.opencast.org/develop/admin/#configuration/admin-ui/statistics/

[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/opencast/opencast-admin-interface:pr-1003

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/opencast/opencast-admin-interface:pr-1003

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.

[github-actions]

This pull request is deployed at test.admin-interface.opencast.org/1003/2024-12-02_15-03-46/ .
It might take a few minutes for it to become available.

[snoesberger]

Thanks for this fix! I have tested this PR with statistics data from our test system and the display of graphs, download etc. works as expected. The code changes look reasonable to me (and are certainly an improvement).