Refactor the async user refreshing to use Oban

Previous implementation could cause duplicate simultaneous profile fetches which is not polite.

lib/pleroma/workers/user_refresh_worker.ex

@@ -0,0 +1,14 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Workers.UserRefreshWorker do
+  use Pleroma.Workers.WorkerHelper, queue: "background", max_attempts: 1, unique: [period: 300]
+
+  alias Pleroma.User
+
+  @impl Oban.Worker
+  def perform(%Job{args: %{"ap_id" => ap_id}}) do
+    User.fetch_by_ap_id(ap_id)
+  end
+end