activitypub: introduce internal fetch service actor

lib/pleroma/application.ex

@@ -140,6 +140,11 @@ def start(_type, _args) do
             id: :federator_init,
             start: {Task, :start_link, [&Pleroma.Web.Federator.init/0]},
             restart: :temporary
+          },
+          %{
+            id: :internal_fetch_init,
+            start: {Task, :start_link, [&Pleroma.Web.ActivityPub.InternalFetchActor.init/0]},
+            restart: :temporary
           }
         ] ++
         streamer_child() ++

lib/pleroma/web/activity_pub/internal_fetch_actor.ex

@@ -0,0 +1,20 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.InternalFetchActor do
+  alias Pleroma.User
+
+  require Logger
+
+  def init do
+    # Wait for everything to settle.
+    Process.sleep(1000 * 5)
+    get_actor()
+  end
+
+  def get_actor do
+    "#{Pleroma.Web.Endpoint.url()}/internal/fetch"
+    |> User.get_or_create_service_actor_by_ap_id("internal.fetch")
+  end
+end