Enable backfilling of attachments without message_attachment rows

ts/sql/Server.ts

@@ -705,6 +705,8 @@ export const DataWriter: ServerWritableInterface = {
   disableFSync,
   enableFSyncAndCheckpoint,
 
+  _testOnlyRemoveMessageAttachments,
+
   // Server-only
 
   removeKnownStickers,
@@ -2720,6 +2722,17 @@ function saveMessageAttachment({
   ).run(values);
 }
 
+function _testOnlyRemoveMessageAttachments(
+  db: WritableDB,
+  timestamp: number
+): void {
+  const [query, params] = sql`
+    DELETE FROM message_attachments
+      WHERE sentAt = ${timestamp};`;
+
+  db.prepare(query).run(params);
+}
+
 function saveMessage(
   db: WritableDB,
   message: ReadonlyDeep<MessageType>,