Participations: Add sort index.

priv/repo/migrations/20190410152859_add_participation_updated_at_index.exs

@@ -0,0 +1,7 @@
+defmodule Pleroma.Repo.Migrations.AddParticipationUpdatedAtIndex do
+  use Ecto.Migration
+
+  def change do
+    create index(:conversation_participations, ["updated_at desc"])
+  end
+end