IAlbumTrack: Add getters for the linked entities ID

So that a caller interested in in the ID doesn't have to fetch the
entire entity

include/medialibrary/IAlbumTrack.h

@@ -43,9 +43,12 @@ class IAlbumTrack
          * @return
          */
         virtual ArtistPtr artist() const = 0;
+        virtual int64_t artistId() const = 0;
         virtual GenrePtr genre() = 0;
+        virtual int64_t genreId() const = 0;
         virtual unsigned int trackNumber() = 0;
         virtual AlbumPtr album() = 0;
+        virtual int64_t albumId() const = 0;
         virtual MediaPtr media() = 0;
         /**
          * @return Which disc this tracks appears on (or 0 if unspecified)

src/AlbumTrack.cpp

@@ -86,6 +86,11 @@ ArtistPtr AlbumTrack::artist() const
     return m_artist.get();
 }
 
+int64_t AlbumTrack::artistId() const
+{
+    return m_artistId;
+}
+
 void AlbumTrack::createTable( sqlite::Connection* dbConnection )
 {
     const std::string req = "CREATE TABLE IF NOT EXISTS " + policy::AlbumTrackTable::Name + "("
@@ -193,6 +198,11 @@ GenrePtr AlbumTrack::genre()
     return m_genre.get();
 }
 
+int64_t AlbumTrack::genreId() const
+{
+    return m_genreId;
+}
+
 bool AlbumTrack::setGenre( std::shared_ptr<Genre> genre )
 {
     // We need to fetch the old genre entity now, in case it gets deleted through
@@ -247,6 +257,11 @@ std::shared_ptr<IAlbum> AlbumTrack::album()
     return m_album.get().lock();
 }
 
+int64_t AlbumTrack::albumId() const
+{
+    return m_albumId;
+}
+
 std::shared_ptr<IMedia> AlbumTrack::media()
 {
     auto lock = m_media.lock();

src/AlbumTrack.h

@@ -60,11 +60,14 @@ class AlbumTrack : public IAlbumTrack, public DatabaseHelpers<AlbumTrack, policy
 
         virtual int64_t id() const override;
         virtual ArtistPtr artist() const override;
+        virtual int64_t artistId() const override;
         virtual GenrePtr genre() override;
+        virtual int64_t genreId() const override;
         bool setGenre( std::shared_ptr<Genre> genre );
         virtual unsigned int trackNumber() override;
         virtual unsigned int discNumber() const override;
         virtual std::shared_ptr<IAlbum> album() override;
+        virtual int64_t albumId() const override;
         virtual std::shared_ptr<IMedia> media() override;
 
         static void createTable( sqlite::Connection* dbConnection );