func wrapUpAlbum(album *model.Album, artist *model.Artist, category *model.Category) {
album.Category = category.Name
if artist != nil {
album.Artist = artist.Name
artist.Albums = append(artist.Albums, album)
} else { // bare album, no artist
category.Albums = append(category.Albums, album)
}
}
func wrapUpArtist(artist *model.Artist, category *model.Category) {
category.Artists = append(category.Artists, artist)
}