Cannot unsubscribe via "Manage Subscription" modal

[ybnd]

Describe the bug

After you've subscribed to a Community or Collection via the "Edit" menu, it is no longer possible to unsubscribe from the same dialog.

To Reproduce

Steps to reproduce the behavior:

1. Log in to DSpace as an administrator
2. Select a random Community or Collection
3. Click "⋮ → Subscribe" to open the subscription dialog and subscribe
4. Open the same dialog again (now called "Manage subscription")
   • You'll see the subscription period you set before
   • Once you unset it, the "Submit" button gets disabled and you cannot save the change

Screen.Recording.2026-07-01.at.11.46.09.mov

Expected behavior

Given that the menu option is now called "Manage subscription", it should be possible to unsubscribe from the same dialog.

Workaround

You can still unsubscribe from /subscriptions

[lgeggleston]

Confirmed this behavior - the change to "Manage Subscription" comes from this related fix in 10.0.. There is also helper text that says "To remove this subscription, please visit the "Subscriptions" page under your user profile". However, I agree that it would be more convenient and make more sense to allow the user to Unsubscribe from the same place.

@guillermo-escire Since you worked on #4283, would you by chance be interested in working on this improvement? And/or, do you know if this question came up during the review process for that (I didn't see anything on a brief look at the comments, but may have missed something)?