Store last fm information into session (doesn't work yet)

lib/music_library_web/controllers/last_fm_controller.ex

@@ -1,7 +1,19 @@
 defmodule MusicLibraryWeb.LastFmController do
   use MusicLibraryWeb, :controller
 
-  def callback(conn, %{"token" => _token}) do
-    conn |> redirect(to: ~p"/")
+  def callback(conn, %{"token" => token}) do
+    case LastFm.get_session(token) do
+      {:ok, session} ->
+        conn
+        |> put_session(:last_fm_user, session.name)
+        |> put_session(:last_fm_key, session.key)
+        |> put_flash(:info, "Successfully authenticated with Last.fm.")
+        |> redirect(to: ~p"/")
+
+      {:error, reason} ->
+        conn
+        |> put_flash(:error, "Failed to authenticate with Last.fm: #{reason}")
+        |> redirect(to: ~p"/")
+    end
   end
 end