Get album info (when available) from Last.fm, add getAlbumInfo endpoint (#2061)

* lastfm album.getInfo, getAlbuminfo(2) endpoints

* ... for description and reduce not found log level

* address first comments

* return all images

* Update migration timestamp

* Handle a few edge cases

* Add CoverArtPriority option to retrieve albumart from external sources

* Make agents methods more descriptive

* Use Last.fm name consistently

Co-authored-by: Deluan <deluan@navidrome.org>

db/migration/20230117180400_add_album_info.go

@@ -0,0 +1,33 @@
+package migrations
+
+import (
+	"database/sql"
+
+	"github.com/pressly/goose"
+)
+
+func init() {
+	goose.AddMigration(upAddAlbumInfo, downAddAlbumInfo)
+}
+
+func upAddAlbumInfo(tx *sql.Tx) error {
+	_, err := tx.Exec(`
+alter table album
+	add description varchar(255) default '' not null;
+alter table album
+	add small_image_url varchar(255) default '' not null;
+alter table album
+	add medium_image_url varchar(255) default '' not null;
+alter table album
+	add large_image_url varchar(255) default '' not null;
+alter table album
+	add external_url varchar(255) default '' not null;
+alter table album
+	add external_info_updated_at datetime;
+`)
+	return err
+}
+
+func downAddAlbumInfo(tx *sql.Tx) error {
+	return nil
+}