fix(server): save snapshot and delete updates in the same transaction (#12856)

close CLOUD-229



#### PR Dependency Tree


* **PR #12856** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Refactor**
- Improved the internal handling of document updates and snapshots to
enhance reliability and maintainability. No changes to user-facing
features or functionality.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/core/doc/storage/doc.ts

@@ -1,4 +1,5 @@
 import { Logger } from '@nestjs/common';
+import { Transactional } from '@nestjs-cls/transactional';
 import {
   applyUpdate,
   diffUpdate,
@@ -78,6 +79,24 @@ export abstract class DocStorageAdapter extends Connection {
     const updates = await this.getDocUpdates(spaceId, docId);
 
     if (updates.length) {
+      return await this.squashUpdatesToSnapshot(
+        spaceId,
+        docId,
+        updates,
+        snapshot
+      );
+    }
+
+    return snapshot;
+  }
+
+  @Transactional()
+  private async squashUpdatesToSnapshot(
+    spaceId: string,
+    docId: string,
+    updates: DocUpdate[],
+    snapshot: DocRecord | null
+  ) {
     this.logger.log(
       `Squashing updates, spaceId: ${spaceId}, docId: ${docId}, updates: ${updates.length}`
     );
@@ -85,8 +104,8 @@ export abstract class DocStorageAdapter extends Connection {
       snapshot ? [snapshot, ...updates] : updates
     );
 
-      const newSnapshot = {
-        spaceId: spaceId,
+    const newSnapshot: DocRecord = {
+      spaceId,
       docId,
       bin,
       timestamp,
@@ -102,18 +121,13 @@ export abstract class DocStorageAdapter extends Connection {
 
     // always mark updates as merged unless throws
     const count = await this.markUpdatesMerged(spaceId, docId, updates);
-      if (count > 0) {
     this.logger.log(
-          `Marked ${count} updates as merged, spaceId: ${spaceId}, docId: ${docId}`
+      `Marked ${count} updates as merged, spaceId: ${spaceId}, docId: ${docId}, timestamp: ${timestamp}`
     );
-      }
 
     return newSnapshot;
   }
 
-    return snapshot;
-  }
-
   async getDocDiff(
     spaceId: string,
     docId: string,