Run Repo vacuum via Oban scheduled job

This way if there's any resource contention to obtain a db connection,
Oban can manage retries.

lib/music_library/worker/repo_vacuum.ex

@@ -0,0 +1,10 @@
+defmodule MusicLibrary.Worker.RepoVacuum do
+  use Oban.Worker, queue: :heavy_writes, max_attempts: 3
+
+  require Logger
+
+  @impl Oban.Worker
+  def perform(_) do
+    MusicLibrary.Repo.vacuum()
+  end
+end