Added playlist repository logic.

Harmonia.Core/Models/Playlist.cs

@@ -3,12 +3,12 @@ using Harmonia.Core.Extensions;
 
 namespace Harmonia.Core.Models;
 
-public class Playlist(string name)
+public class Playlist
 {
     private readonly List<PlaylistSong> _songs = [];
 
     public string UID { get; init; } = Guid.NewGuid().ToString();
-    public string Name { get; set; } = name;
+    public string? Name { get; set; }
     public IReadOnlyList<PlaylistSong> Songs => _songs;
     public List<GroupOption> GroupOptions { get; set; } = [];
     public List<SortOption> SortOptions { get; set; } = [];