Add config endpoint

lib/mobilizon_web/schema/config.ex

@@ -0,0 +1,23 @@
+defmodule MobilizonWeb.Schema.ConfigType do
+  @moduledoc """
+  Schema representation for User
+  """
+  use Absinthe.Schema.Notation
+
+  alias MobilizonWeb.Resolvers.Config
+
+  @desc "A config object"
+  object :config do
+    # Instance name
+    field(:name, :string)
+
+    field(:registrations_open, :boolean)
+  end
+
+  object :config_queries do
+    @desc "Get the instance config"
+    field :config, :config do
+      resolve(&Config.get_config/3)
+    end
+  end
+end