auth.php: disallow unencrypted logins by default

inc/functions/net.php

@@ -0,0 +1,10 @@
+<?php
+namespace Vichan\Functions\Net;
+
+
+/**
+ * @return bool Returns if the client-server connection is an encrypted one (HTTPS).
+ */
+function is_connection_secure(): bool {
+	return !empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != 'off';
+}