Fix group cancel button

[priya-tik]

This PR adds missing cancel functionality to the Group Details wizard modal. Previously, the cancel button was non-functional due to the absence of a callback handler. This update ensures a smooth user experience by allowing users to exit the modal properly.

[github-actions]

Hi @priya-tik
Thank you for contributing to the Opencast Admin UI.
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[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-1204

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-1204

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/1204/2025-05-17_06-36-28/ .
It might take a few minutes for it to become available.

[priya-tik]

@Arnei Please add the bug or enhancement labels to this PR. Thank you!

[Piriya-VM]

The cancel button works now. :) I didn't do a code review!

[NadiaUoM]

This PR commits content the fix for below PR's as well:

#1200
#1197

[github-actions]

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

[lkiesow]

Apart from this having conflicts, it's very confusing that you created multiple pull requests all with the same code.
Can you split them apart and create one pull request for one patch, please?
It's basically creating a new branch per pull request and then using that to create the pull request.

[github-actions]

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

[NadiaUoM]

@Arnei : I think we should close this PR also since the changes for this issue has been already merged...

#1277

[Arnei]

Seems so, closing this. Still, thanks for working on this priya-tik!