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

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

lib/mobilizon/medias/media.ex

@@ -0,0 +1,40 @@
+defmodule Mobilizon.Medias.Media do
+  @moduledoc """
+  Represents a media entity.
+  """
+
+  use Ecto.Schema
+
+  import Ecto.Changeset, only: [cast: 3, cast_embed: 2]
+
+  alias Mobilizon.Actors.Actor
+  alias Mobilizon.Discussions.Comment
+  alias Mobilizon.Events.Event
+  alias Mobilizon.Medias.File
+  alias Mobilizon.Posts.Post
+
+  @type t :: %__MODULE__{
+          file: File.t(),
+          actor: Actor.t()
+        }
+
+  schema "medias" do
+    embeds_one(:file, File, on_replace: :update)
+    belongs_to(:actor, Actor)
+    has_many(:event_picture, Event, foreign_key: :picture_id)
+    many_to_many(:events, Event, join_through: "events_medias")
+    has_many(:posts_picture, Post, foreign_key: :picture_id)
+    many_to_many(:posts, Post, join_through: "posts_medias")
+    many_to_many(:comments, Comment, join_through: "comments_medias")
+
+    timestamps()
+  end
+
+  @doc false
+  @spec changeset(t, map) :: Ecto.Changeset.t()
+  def changeset(%__MODULE__{} = media, attrs) do
+    media
+    |> cast(attrs, [:actor_id])
+    |> cast_embed(:file)
+  end
+end