fix(sync): keep yjs file during sync session cleanup

Even if all sessions have expired and been removed
there may still be disconnected clients
that hold state from the last editing session.

When they reconnect they will send their yjs updates
based on the old state they had.
Preserve the yjs state accross editing sessions
so updates send after a reconnect can still be processed.

Signed-off-by: Max <max@nextcloud.com>

lib/Service/DocumentService.php

@@ -420,7 +420,9 @@ public function resetDocument(int $documentId, bool $force = false): void {
 			$this->sessionMapper->deleteByDocumentId($documentId);
 			$this->documentMapper->delete($document);
 
-			$this->getStateFile($documentId)->delete();
+			if ($force) {
+				$this->getStateFile($documentId)->delete();
+			}
 			$this->logger->debug('document reset for ' . $documentId);
 		} catch (DoesNotExistException|NotFoundException $e) {
 			// Ignore if document not found or state file not found