When setting cookies via PHP, add handling of the "path" value in the options (session.php)

Otherwise, cookies set via PHP will not be able to be changed in JS.
Because JS saves cookies with path="/"
Closed: #4024

web/includes/session.php

@@ -1,6 +1,9 @@
 <?php
 // Wrapper around setcookie that auto-sets samesite, and deals with older versions of php
 function zm_setcookie($cookie, $value, $options=array()) {
+  if (!isset($options['path'])) {
+    $options['path'] = '/';
+  }
   if (!isset($options['expires'])) {
     $options['expires'] = time()+3600*24*30*12*10; // 10 years?!
   }