Introduce comments below events

Also add tomstones

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

priv/repo/migrations/20191122154018_add_deleted_at_on_comments.exs

@@ -0,0 +1,21 @@
+defmodule Mobilizon.Storage.Repo.Migrations.AddDeletedAtOnComments do
+  use Ecto.Migration
+
+  def up do
+    drop_if_exists(constraint(:comments, "comments_actor_id_fkey"))
+
+    alter table(:comments) do
+      add(:deleted_at, :utc_datetime, null: true)
+      modify(:actor_id, references(:actors, on_delete: :nilify_all), null: true)
+    end
+  end
+
+  def down do
+    drop_if_exists(constraint(:comments, "comments_actor_id_fkey"))
+
+    alter table(:comments) do
+      remove(:deleted_at)
+      modify(:actor_id, references(:actors, on_delete: :nilify_all), null: false)
+    end
+  end
+end