Add a mix task to generate a sitemap

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

lib/mix/tasks/mobilizon/site_map.ex

@@ -0,0 +1,21 @@
+defmodule Mix.Tasks.Mobilizon.SiteMap do
+  @moduledoc """
+  Task to generate a new Sitemap
+  """
+  use Mix.Task
+
+  alias Mix.Tasks.Mobilizon.Common
+  alias Mobilizon.Service.SiteMap
+  alias Mobilizon.Web.Endpoint
+
+  @preferred_cli_env "prod"
+
+  @shortdoc "Generates a new Sitemap"
+  def run(["generate"]) do
+    Common.start_mobilizon()
+
+    with {:ok, :ok} <- SiteMap.generate_sitemap() do
+      Mix.shell().info("Sitemap saved to #{Endpoint.url()}/sitemap.xml")
+    end
+  end
+end