Use stored scrobbled tracks

lib/last_fm/import.ex

@@ -1,28 +1,7 @@
 defmodule LastFm.Import do
-  @insertable_fields [
-    :musicbrainz_id,
-    :title,
-    :artist,
-    :album,
-    :cover_url,
-    :scrobbled_at_uts,
-    :scrobbled_at_label,
-    :last_fm_data
-  ]
-
   def batch(opts) do
     with {:ok, tracks} <- LastFm.get_tracks(opts) do
-      track_params =
-        tracks
-        |> Enum.map(fn t -> Map.take(t, @insertable_fields) end)
-        |> Enum.map(&Map.to_list/1)
-
-      # HACK: if two tracks happen to have the exact same scrobbled_at_uts,
-      # we move it by a sec.
-      MusicLibrary.Repo.insert_all(LastFm.Track, track_params,
-        on_conflict: :nothing,
-        conflict_target: [:scrobbled_at_uts, :title]
-      )
+      LastFm.Feed.update(tracks)
     end
   end
 end