Update guide to add example for cleaning up leftover publications in database upgrade guide and ensure caution message formatting is consistent.(#368)

Co-authored-by: raj <raj@turbot.com>

Author: RahulSrivastav14

docs/guides/hosting-guardrails/disaster-recovery/database-upgrade/index.md

@@ -260,7 +260,7 @@ In a new session, initiate the `pg_dump` process using the `snapshot ID` obtaine
 nohup time pg_dump -h $SOURCE -U master --snapshot="00000062-000182C4-1" -F c -b -v -f data.dump turbot > dump.log 2>&1 &
 ```
 
- > [!CAUTION] 
+ > [!CAUTION]
  > Enabling logical replication before a long pg_dump/restore can lead to WAL buildup and storage exhaustion. It is recommended to enable RDS storage autoscaling to prevent out-of-space errors during migration.
 ### Monitor
 
@@ -523,7 +523,7 @@ Run smoke tests to Test both the restored and new database instances to confirm
 <!-- TO CHECK IF THIS WILL TERMINATE THE OLD RDS INSTANCE turbot-einstein-blue? -->
 <!-- INCLUDE TERMINATION PROTECTION NOTE HERE FOR RDS INSTANCE -->
 
-Delete the new TED stack i.e. `turbot-einstein-green` along with its associated resources, including the S3 bucket, log groups, and AWS Backup. Clean up replication slots and subscriptions.
+After verifying a successful upgrade and switchover, delete the new TED stack i.e `turbot-einstein-green` and remove its associated resources such as the S3 bucket, CloudWatch log groups, and AWS Backup configurations. Clean up replication slots and subscriptions.
 
 <!-- When the old DB is terminated from the TED stack, the following will be automatically cleaned up.
 
@@ -533,11 +533,66 @@ select * from pg_replication_slots;
 select * from pg_drop_replication_slot('rs_blue');
 drop schema migration_turbot cascade; -->
 
+### In Case of Upgrade Failure or Aborted Migration
+
+If the database upgrade fails or is manually aborted before completion, it’s important to clean up replication artifacts from the **source database** to avoid lingering replication objects and ensure a clean state for future upgrade attempts.
+
+Run the following SQL commands on the source (blue) database to drop replication artifacts:
+
+```sql
+-- Check for existing publications
+SELECT * FROM pg_publication;
+
+-- Drop the publication used for replication
+DROP PUBLICATION pub_blue;
+
+-- Check for replication slots
+SELECT * FROM pg_replication_slots;
+
+-- Drop the replication slot used for streaming
+SELECT * FROM pg_drop_replication_slot('rs_blue');
+
+-- Check for existing subscriptions
+SELECT * FROM pg_subscription;
+
+-- Drop the subscription created during upgrade
+DROP SUBSCRIPTION sub_blue;
+```
+
+**Example:**
+
+Here's an example showing how to check for and clean up a leftover publication:
+
+`select * from pg_publication` indicates the presence of left over `PUBLICATION` `pub_blue`, this needs to be dropped. Recheck after dropping the `PUBLICATION`
+
+```
+turbot=> select * from pg_publication
+turbot-> ;
+    oid     | pubname  | pubowner | puballtables | pubinsert | pubupdate | pubdelete | pubtruncate | pubviaroot
+------------+----------+----------+--------------+-----------+-----------+-----------+-------------+------------
+ 2142597123 | pub_blue |    16397 | t            | t         | t         | t         | t           | f
+(1 row)
+
+turbot=> DROP PUBLICATION pub_blue;
+DROP PUBLICATION
+
+turbot=> select * from pg_publication
+;
+ oid | pubname | pubowner | puballtables | pubinsert | pubupdate | pubdelete | pubtruncate | pubviaroot
+-----+---------+----------+--------------+-----------+-----------+-----------+-------------+------------
+(0 rows)
+```
+
+Also, make sure to delete associated resources created as part of the upgrade attempt:
+- S3 bucket
+- CloudWatch Log Groups
+- AWS Backup plans and vaults
+- Any temporary RDS instances or TED-related infrastructure
+
 ## Step 18: Disable and Delete Subscriptions
 
 Disable and delete subscription and replication slots.
 
-
 ```sql
 select * from pg_subscription;
 alter subscription sub_blue disable;