add basic playlist

server/ctrlsubsonic/spec/construct.go

@@ -0,0 +1,11 @@
+package spec
+
+import "senan.xyz/g/gonic/model"
+
+func NewPlaylist(p *model.Playlist) *Playlist {
+	return &Playlist{
+		ID:      p.ID,
+		Name:    p.Name,
+		Comment: p.Comment,
+	}
+}