Improve PlaybackManager stability, added PlaybackBar

- PlaybackManager now takes ownership of set items
- PlaybackManager can play items just by their itemId, avoids useless
  item creation on the QML side of things.
- Allow calling Jellyfin::registerTypes with a different URI
- Minor code cleanup

core/include/JellyfinQt/jellyfin.h

@@ -10,7 +10,7 @@
 #include "JellyfinQt/jellyfinplaybackmanager.h"
 
 namespace Jellyfin {
-void registerTypes();
+void registerTypes(const char *uri = "nl.netsoj.chris.Jellyfin");
 }
 
 #endif // JELLYFIN_H

core/include/JellyfinQt/jellyfinitem.h

@@ -302,6 +302,7 @@ class Item : public RemoteData {
     Q_OBJECT
 public:
     Q_INVOKABLE explicit Item(QObject *parent = nullptr);
+    Item(QString itemId, ApiClient *apiClient, QObject *parent = nullptr);
 
     Q_PROPERTY(QString jellyfinId READ jellyfinId WRITE setJellyfinId NOTIFY jellyfinIdChanged)
 
@@ -473,7 +474,7 @@ protected:
     QString getDataUrl() const override;
     bool canReload() const override;
 
-    QString m_id;
+    QString m_id = QStringLiteral("");
     QString m_name;
     QString m_originalTitle;
     QString m_serverId;

core/include/JellyfinQt/jellyfinplaybackmanager.h

@@ -89,6 +89,12 @@ signals:
 
 public slots:
     void updatePlaybackInfo();
+    /**
+     * @brief playItem Plays the item with the given id. This will construct the Jellyfin::Item internally
+     * and delete it later.
+     * @param itemId The id of the item to play.
+     */
+    void playItem(const QString &itemId);
 private slots:
     void mediaPlayerStateChanged(QMediaPlayer::State newState);
     void mediaPlayerPositionChanged(qint64 position);