remove PurgeExpiredActivity from Oban db config

priv/repo/migrations/20201113060459_remove_purge_expired_activity_worker_from_oban_config.exs

@@ -0,0 +1,19 @@
+defmodule Pleroma.Repo.Migrations.RemovePurgeExpiredActivityWorkerFromObanConfig do
+  use Ecto.Migration
+
+  def change do
+    with %Pleroma.ConfigDB{} = config <-
+           Pleroma.ConfigDB.get_by_params(%{group: :pleroma, key: Oban}),
+         crontab when is_list(crontab) <- config.value[:crontab],
+         index when is_integer(index) <-
+           Enum.find_index(crontab, fn {_, worker} ->
+             worker == Pleroma.Workers.Cron.PurgeExpiredActivitiesWorker
+           end) do
+      updated_value = Keyword.put(config.value, :crontab, List.delete_at(crontab, index))
+
+      config
+      |> Ecto.Changeset.change(value: updated_value)
+      |> Pleroma.Repo.update()
+    end
+  end
+end