Fix extensions in actualize_script (#5243)

* Fix extension freshrss_user_maintenance in actualize_script
Follow-up of https://github.com/FreshRSS/FreshRSS/pull/3440

The hook was called before registering all the extensions for the current user

* PHPStan Level 6 for extensions
And remove 5-year old legacy format of enabled extensions < FreshRSS 1.11.1

* Fix multiple bugs in extensions

* Minor typing

* Don't change signature of methods supposed to be overridden

* PHPStan Level 9 and compatibility Intelliphense

* Set as final the methods not supposed to be overriden

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/core-extensions/Google-Groups/extension.php b/lib/core-extensions/Google-Groups/extension.php
index 656bf9b8f..cdd605cd9 100644
--- a/lib/core-extensions/Google-Groups/extension.php
+++ b/lib/core-extensions/Google-Groups/extension.php
@@ -1,10 +1,11 @@
 <?php
 class GoogleGroupsExtension extends Minz_Extension {
+	/** @return void */
 	public function init() {
 		$this->registerHook('check_url_before_add', array('GoogleGroupsExtension', 'findFeed'));
 	}
 
-	public static function findFeed($url) {
+	public static function findFeed(string $url): string {
 		return preg_replace('%^(https?://groups.google.com/forum)/#!forum/(.+)$%i', '$1/feed/$2/msgs/rss.xml', $url);
 	}
 }