Add change password option

[Arnei]

Fixes #356.

Adds a new button in the user menu (the dropdown in the top right corner) that allows users to change their own password. The idea is to allow users to change their password without having to give them full access to the users table.

Requires a new endpoint: opencast/opencast#7646

How to test this

Requires an Opencast with the backend PR linked above.

[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/admin-interface:pr-1604

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/admin-interface:pr-1604

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/1604/2026-05-11_11-50-20/ .
It might take a few minutes for it to become available.

[mtneug]

For some users, changing the password is not possible. admin usually is an in-memory user with a password defined in a configuration file. Users logging in through an SSO system also shouldn't be able to change their password. Really, only JPA users should have the option. Is this already considered by the frontend?

[Arnei]

This is considered by the frontend insofar as that a non-"manageable" user cannot change their password. Same as for the users table, where you cannot change a non-manageable user. I am not certain that "non-manageable" is the same as "only JPA", but I would expect it to be.

[mtneug]

Nice. I think this is the correct check. At least admin and user references are non-"manageable".