Refactor adding tags to an event

Also refactor extracting tags from content, now uses Pleroma's Formatter

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

lib/mobilizon_web/resolvers/tag.ex

@@ -2,7 +2,7 @@ defmodule MobilizonWeb.Resolvers.Tag do
   @moduledoc """
   Handles the tag-related GraphQL calls
   """
-  require Logger
+  alias Mobilizon.Events
   alias Mobilizon.Events.Event
   alias Mobilizon.Events.Tag
 
@@ -19,6 +19,15 @@ defmodule MobilizonWeb.Resolvers.Tag do
     {:ok, Mobilizon.Events.list_tags_for_event(id)}
   end
 
+  @doc """
+  Retrieve the list of tags for an event
+  """
+  def list_tags_for_event(%{url: url}, _args, _resolution) do
+    with %Event{id: event_id} <- Events.get_event_by_url(url) do
+      {:ok, Mobilizon.Events.list_tags_for_event(event_id)}
+    end
+  end
+
   #  @doc """
   #  Retrieve the list of related tags for a given tag ID
   #  """