Movie Set Collections don't create subdirectory for each collection

[mihawk90]

Describe the bug Movie Set Collections don't create subdirectories for each collection when the "Separate artwork directory" option is used. This means that inevitably multiple collections are using the same artwork, and changing the artwork for a second collection also changes it for the first because it overwrites the file.

To Reproduce Steps to reproduce the behavior:

1. Import some movies with different Sets/Collections
2. Open the Movie Sets list
3. Select a Movie Set and change the artwork, then save
4. Select a second Movie Set and notice the artwork from the first set showing there
5. Change the artwork on the second set, then save
6. Go back to the first set and notice the artwork changed

Expected behavior Each collection should create its own subdirectory for their respective artwork.

Ideally the naming convention for this should be able to be changed by the user, either through regular settings or the advancedsettings.xml (Jellyfin for example appends [boxset] to collection names, e.g. Jumanji Collection [boxset]).

Screenshots

 pwd
/mnt/tank/media/collections
 ls -1
backdrop.jpg
'Fantastic Four Collection [boxset]'
'Jumanji Collection [boxset]'
'Madagascar Collection [boxset]'
'The Bourne Collection [boxset]'
'The Fast and the Furious Collection [boxset]'
'The Lord of the Rings Collection [boxset]'
'The Matrix Collection [boxset]'
'X-Men Collection [boxset]'

Note these directories were created by Jellyfin, so they are unrelated to ME (and also not being read).

MediaElch Version:

• [ ] 2.12.1-dev (nightly)
• [x] 2.12.0 (stable)

Operating System:

• [ ] Windows
• [ ] macOS
• [x] Linux (distribution: Fedora 40 KDE)