CLC Sync: add remove feature #638
Description
It is not possible from the UI to remove a link. It already happened multiple times that the book is removed or is not existing in CLC and the link is broken.
The library should be able to remove it.
On top of that, the admin panel for the CLC sync is not helpful: it shows the parent record ID, but we normally search with the current record ID, which always leads to empty search results.