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

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

lib/mobilizon/medias/file.ex

@@ -0,0 +1,38 @@
+defmodule Mobilizon.Medias.File do
+  @moduledoc """
+  Represents a file entity.
+  """
+
+  use Ecto.Schema
+
+  import Ecto.Changeset, only: [cast: 3, validate_required: 2]
+
+  @type t :: %__MODULE__{
+          name: String.t(),
+          url: String.t(),
+          content_type: String.t(),
+          size: integer
+        }
+
+  @required_attrs [:name, :url]
+  @optional_attrs [:content_type, :size]
+  @attrs @required_attrs ++ @optional_attrs
+
+  @derive Jason.Encoder
+  embedded_schema do
+    field(:name, :string)
+    field(:url, :string)
+    field(:content_type, :string)
+    field(:size, :integer)
+
+    timestamps()
+  end
+
+  @doc false
+  @spec changeset(t, map) :: Ecto.Changeset.t()
+  def changeset(%__MODULE__{} = file, attrs) do
+    file
+    |> cast(attrs, @attrs)
+    |> validate_required(@required_attrs)
+  end
+end