Fallback to sent_at when serverTimestamp is empty

Co-authored-by: Fedor Indutny <79877362+indutny-signal@users.noreply.github.com>

ts/util/deleteForEveryone.ts

@@ -11,16 +11,19 @@ export async function deleteForEveryone(
   doe: DeleteModel,
   shouldPersist = true
 ): Promise<void> {
+  const messageTimestamp =
+    message.get('serverTimestamp') || message.get('sent_at') || 0;
+
   // Make sure the server timestamps for the DOE and the matching message
   // are less than one day apart
-  const delta = Math.abs(
-    doe.get('serverTimestamp') - (message.get('serverTimestamp') || 0)
-  );
+  const delta = Math.abs(doe.get('serverTimestamp') - messageTimestamp);
+
   if (delta > ONE_DAY) {
     window.log.info('Received late DOE. Dropping.', {
       fromId: doe.get('fromId'),
       targetSentTimestamp: doe.get('targetSentTimestamp'),
       messageServerTimestamp: message.get('serverTimestamp'),
+      messageSentAt: message.get('sent_at'),
       deleteServerTimestamp: doe.get('serverTimestamp'),
     });
     return;