MetadataParser: Let thumbnail helpers insert the thumbnail
MetadataParser: Let thumbnail helpers insert the thumbnail

Instead of doing it inconditionally, we let Thumbnail::updateOrReplace
handle the insertion in database.
This prevents inserting a thumbnail in database if it isn't actually
used by any entity

chouquette/medialibrary,chouquette/medialibrary,chouquette/medialibrary,chouquette/medialibrary