[TASK]: Replace unsubscribe service with takeUntilDestroyed

[correct-horse-battery-bench]

Description

There exists an unsubscribe service (web-ui/src/app/core/_services/unsubscribe.service.ts)
which can be replaced with takeUntilDestroyed pipe and injected DestroyRef.

This pattern isn't needed anymore since rxjs included this pipe.

Also check in general if all observables use this in its pipe. For certain observables (route based usually) it is not strictly necessary anymore to unsubscribe as this will automatically done by the router. Other observables still need to be unsubscribed manually (or with this pipe) in order to prevent memory leaks.