refactor: New Session class

So that session is shared between classes and does not get overwritten

classes/SessionManager.php

@@ -0,0 +1,37 @@
+<?php
+/**
+ * SessionManager class.
+ */
+
+namespace Alltube;
+
+use Aura\Session\Session;
+use Aura\Session\SessionFactory;
+
+/**
+ * Manage sessions.
+ */
+class SessionManager
+{
+
+    /**
+     * Current session.
+     *
+     * @var Session
+     */
+    private static $session;
+
+    /**
+     * Get the current session.
+     *
+     * @return Session
+     */
+    public static function getSession()
+    {
+        if (!isset(self::$session)) {
+            $session_factory = new SessionFactory();
+            self::$session = $session_factory->newInstance($_COOKIE);
+        }
+        return self::$session;
+    }
+}