Prevent backslash in class name

since the default code is using get_called_class, you can end up with \ in the class name which is an escape character for css selectors
this update convert for example

even valCMS_ACCESS_SilverStripe\VersionedAdmin\ArchiveAdmin
to
even valCMS_ACCESS_SilverStripe-VersionedAdmin-ArchiveAdmin

ArchiveAdmin class should probably implement     private static $required_permission_codes = 'CMS_ACCESS_ArchiveAdmin '; also

src/Security/PermissionCheckboxSetField.php

@@ -207,7 +207,7 @@ public function Field($properties = [])
 
                     $odd = ($odd + 1) % 2;
                     $extraClass = $odd ? 'odd' : 'even';
-                    $extraClass .= ' val' . str_replace(' ', '', $code ?? '');
+                    $extraClass .= ' val' . str_replace([' ', '\\'], ['', '-'], $code ?? '');
                     $itemID = $this->ID() . '_' . preg_replace('/[^a-zA-Z0-9]+/', '', $code ?? '');
                     $disabled = $inheritMessage = '';
                     $checked = (isset($uninheritedCodes[$code]) || isset($inheritedCodes[$code]))