Formalize search_release_by_barcode/2 callback

lib/music_brainz/api_behaviour.ex

@@ -2,6 +2,7 @@ defmodule MusicBrainz.APIBehaviour do
   @type musicbrainz_id :: String.t()
   @type config :: MusicBrainz.Config.t()
   @type limit :: pos_integer()
+  @type barcode :: String.t()
 
   @callback get_release_group(musicbrainz_id, config) :: {:ok, map()} | {:error, String.t()}
 
@@ -12,6 +13,8 @@ defmodule MusicBrainz.APIBehaviour do
   @callback search_release_group(String.t(), Keyword.t(), config) ::
               {:ok, [map()]} | {:error, String.t()}
 
+  @callback search_release_by_barcode(barcode, config) :: {:ok, [map()]} | {:error, String.t()}
+
   @callback get_cover_art({:musicbrainz_id, musicbrainz_id()} | {:url, String.t()}, config) ::
               {:ok, binary()} | {:error, String.t()}
 end

lib/music_brainz/api_impl.ex

@@ -305,6 +305,7 @@ defmodule MusicBrainz.APIImpl do
     json_get(url, config)
   end
 
+  @impl true
   def search_release_by_barcode(barcode, config) do
     url =
       @base_url <> "/release?query=barcode:#{barcode}&fmt=json"