Start to implement the save_all method.

backend/infrastructure/src/video/adapter.rs

@@ -100,6 +100,11 @@ impl VideoPort for LibraryItemAdapter {
     }
 
     fn save_all(&self, library_items: &Vec<LibraryItem>) -> Result<(), VideoError> {
+        let entities = library_items.iter()
+            .map(LibraryItemEntity::from_library_item)
+            .collect::<Vec<LibraryItemEntity>>();
+        
+        self.repository.save_all(entities)?;
         Ok(())
     }