feat: Catch callback exception in callForSeenUsers

In case of large instances, `callForSeenUsers()` can take a lot of time to finish.

The new arguments give the opportunity for the caller to set a time limit, and to start from a given offset. The method now also returns the offset if it was stopped early.

Signed-off-by: Louis Chemineau <louis@chmn.me>

Author: artonge

lib/private/User/Manager.php

@@ -637,9 +637,13 @@ public function callForSeenUsers(\Closure $callback, int|null $maxTime, int $off
 				foreach ($this->backends as $backend) {
 					if ($backend->userExists($userId)) {
 						$user = $this->getUserObject($userId, $backend, false);
-						$return = $callback($user);
-						if ($return === false) {
-							return 0;
+						try {
+							$return = $callback($user);
+							if ($return === false) {
+								return 0;
+							}
+						} catch (\Throwable $e) {
+							$this->logger->error('Error while calling callback for seen users', ['exception' => $e, 'userId' => $userId, 'backend' => $backend::class]);
 						}
 						break;
 					}