parser: Item: Rework subitems creation

Delegate subitem creation to the parent item. This way we can access the
internals of the parent item upon creation, and the item is created in
place.
This will also ease up privatization of the Item type, since we don't
want it to be publicly available for creation

src/metadata_services/vlc/VLCMetadataService.cpp

@@ -192,9 +192,8 @@ void VLCMetadataService::mediaToItem( VLC::Media& media, parser::Task::Item& ite
             assert( vlcMedia != nullptr );
             // Always add 1 to the playlist/subitem index, as 0 is an invalid index
             // in this context
-            parser::Task::Item subItem{ vlcMedia->mrl(), i + 1u };
+            parser::Task::Item& subItem = item.createSubItem( vlcMedia->mrl(), i + 1u );
             mediaToItem( *vlcMedia, subItem );
-            item.addSubItem( std::move( subItem ) );
         }
     }
 }

src/parser/Task.cpp

@@ -185,9 +185,10 @@ const std::vector<Task::Item>& Task::Item::subItems() const
     return m_subItems;
 }
 
-void Task::Item::addSubItem( Task::Item item )
+Task::Item& Task::Item::createSubItem( std::string mrl, unsigned int playlistIndex )
 {
-    m_subItems.emplace_back( std::move( item ) );
+    m_subItems.emplace_back( std::move( mrl ), playlistIndex );
+    return m_subItems.back();
 }
 
 int64_t Task::Item::duration() const

src/parser/Task.h

@@ -161,7 +161,7 @@ public:
         void setMrl( std::string mrl );
 
         const std::vector<Item>& subItems() const;
-        void addSubItem( Item mrl );
+        Item& createSubItem( std::string mrl, unsigned int playlistIndex );
 
         int64_t duration() const;
         void setDuration( int64_t duration );