activity: add recipients_to and recipients_cc fields

priv/repo/migrations/20180829082446_add_recipients_to_and_cc_fields_to_activities.exs

@@ -0,0 +1,13 @@
+defmodule Pleroma.Repo.Migrations.AddRecipientsToAndCcFieldsToActivities do
+  use Ecto.Migration
+
+  def change do
+    alter table(:activities) do
+      add :recipients_to, {:array, :string}
+      add :recipients_cc, {:array, :string}
+    end
+
+    create index(:activities, [:recipients_to], using: :gin)
+    create index(:activities, [:recipients_cc], using: :gin)
+  end
+end