User gets logged out without feedback when same account is used elsewhere

[alegontarz]

Describe the bug

When using an account that is also being used by someone else, the system sometimes logs out the user silently. there's no notification or feedback about the session ending. the user remains on the page and can interact with the UI, but many actions result in unexplained errors. only after refreshing the page is it clear that the user has been logged out.

To Reproduce

Steps to reproduce the behavior:
Hard to reproduce, it happens randomly.

Expected behavior

If a session ends (e.g. due to logging in elsewhere), the user should immediately receive a visible message or be redirected to the login screen.

[tdonohue]

This is a duplicate of DSpace/DSpace#3257 . This behavior occurs because only one active session is supported per user account. More details can be found in that ticket