Track usage of media files and add a job to clean them

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

priv/repo/migrations/20201124094655_add_media_tables.exs

@@ -0,0 +1,22 @@
+defmodule Mobilizon.Storage.Repo.Migrations.AddMediaTables do
+  use Ecto.Migration
+
+  def change do
+    rename(table(:pictures), to: table(:medias))
+
+    create table(:events_medias, primary_key: false) do
+      add(:event_id, references(:events, on_delete: :delete_all), primary_key: true)
+      add(:media_id, references(:medias, on_delete: :delete_all), primary_key: true)
+    end
+
+    create table(:posts_medias, primary_key: false) do
+      add(:post_id, references(:posts, on_delete: :delete_all, type: :uuid), primary_key: true)
+      add(:media_id, references(:medias, on_delete: :delete_all), primary_key: true)
+    end
+
+    create table(:comments_medias, primary_key: false) do
+      add(:comment_id, references(:comments, on_delete: :delete_all), primary_key: true)
+      add(:media_id, references(:medias, on_delete: :delete_all), primary_key: true)
+    end
+  end
+end