Use map_join instead of map+join

lib/music_brainz/release_group_search_result.ex

@@ -9,10 +9,7 @@ defmodule MusicBrainz.ReleaseGroupSearchResult do
       id: rg["id"],
       type: ReleaseGroup.parse_type(rg["primary-type"]),
       title: rg["title"],
-      artists:
+      artists: Enum.map_join(rg["artist-credit"], ", ", fn ac -> ac["artist"]["name"] end),
-        rg["artist-credit"]
-        |> Enum.map(fn ac -> ac["artist"]["name"] end)
-        |> Enum.join(", "),
       release: rg["first-release-date"]
     }
   end

lib/music_brainz/release_search_result.ex

@@ -9,10 +9,7 @@ defmodule MusicBrainz.ReleaseSearchResult do
       id: r["id"],
       title: r["title"],
       release_group: parse_release_group(r["release-group"]),
-      artists:
+      artists: Enum.map_join(r["artist-credit"], ", ", fn ac -> ac["artist"]["name"] end),
-        r["artist-credit"]
-        |> Enum.map(fn ac -> ac["artist"]["name"] end)
-        |> Enum.join(", "),
       date: r["date"],
       barcode: r["barcode"],
       media: parse_media(r["media"])

lib/music_library/records.ex

@@ -147,10 +147,7 @@ defmodule MusicLibrary.Records do
   end
 
   def populate_genres(record) do
-    artists =
+    artists = Enum.map_join(record.artists, ",", fn a -> a.name end)
-      record.artists
-      |> Enum.map(fn a -> a.name end)
-      |> Enum.join(",")
 
     completion = %OpenAI.Completion{
       content: """