fix(save): autosave only every ten seconds

Abort autosave if another save is still under way.
We observed save requests taking up to 30 seconds.
In this timespan autosave requests would still be processed
as the lastSavedTime in the database has not been updated yet.

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

Author: max-nextcloud

lib/Service/DocumentService.php

@@ -385,6 +385,11 @@ public function autosave(Document $document, File $file, int $version, string $a
 
 		$this->assertNoOutsideConflict($document, $file, $force);
 
+		// Abort autosave if already saving.
+		if ($this->cache->get('document-save-lock-' . $documentId) && $manualSave === false) {
+			return $document;
+		}
+
 		// Do not save if newer version already saved
 		// Note that $version is the version of the steps the client has fetched.
 		// It may have added steps on top of that - so if the versions match we still save.