Introduce instances admin page

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

lib/mobilizon/instances/instance.ex

@@ -0,0 +1,19 @@
+defmodule Mobilizon.Instances.Instance do
+  @moduledoc """
+  An instance representation
+
+  Using a MATERIALIZED VIEW underneath
+  """
+  use Ecto.Schema
+
+  @primary_key {:domain, :string, []}
+  schema "instances" do
+    field(:event_count, :integer)
+    field(:person_count, :integer)
+    field(:group_count, :integer)
+    field(:followers_count, :integer)
+    field(:followings_count, :integer)
+    field(:reports_count, :integer)
+    field(:media_size, :integer)
+  end
+end