Count unique catalog entries in collection summary

The record_count now reflects the number of grouped catalog lines
the model sees, not raw DB rows. Two copies of the same album on
different formats count as 1 catalog entry.

lib/music_library/collection.ex

@@ -203,16 +203,15 @@ defmodule MusicLibrary.Collection do
       )
       |> Repo.all()
 
-    record_count = length(records)
-
-    summary =
+    groups =
       records
       |> Enum.group_by(& &1.musicbrainz_id)
       |> Enum.map(fn {_id, group} -> format_group(group) end)
       |> Enum.sort()
-      |> Enum.join("\n")
 
-    {summary, record_count}
+    summary = Enum.join(groups, "\n")
+
+    {summary, length(groups)}
   end
 
   defp format_group(records) do

test/music_library/collection_test.exs

@@ -366,7 +366,7 @@ defmodule MusicLibrary.CollectionTest do
       {summary, record_count} = Collection.collection_summary()
       lines = String.split(summary, "\n")
 
-      assert record_count == 2
+      assert record_count == 1
       assert length(lines) == 1
       assert hd(lines) =~ "cd/vinyl"
     end