docs: Add /healthz/readiness endpoint (n8n-io#2455)

Co-authored-by: Kate Mueller <[email protected]>

Author: ivov

docs/hosting/logging-monitoring/monitoring.md

@@ -6,19 +6,27 @@ contentType: howto
 
 # Monitoring
 
-There are two API endpoints you can call to check the status of your instance: `/healthz` and `/metrics`.
+There are three API endpoints you can call to check the status of your instance: `/healthz`, `healthz/readiness`, and `/metrics`.
 
 <!-- vale off -->
-## healthz
+## healthz and healthz/readiness
 <!-- vale on -->
-The `/healthz` endpoint returns a standard HTTP status code. 200 indicates the instance is reachable. It's available for both self-hosted and Cloud users.
+The `/healthz` endpoint returns a standard HTTP status code. 200 indicates the instance is reachable. It doesn't indicate DB status. It's available for both self-hosted and Cloud users.
 
 Access the endpoint:
 
 ```
 <your-instance-url>/healthz
 ```
 
+The `/healthz/readiness` endpoint is similar to the `/healthz` endpoint, but it returns a HTTP status code of 200 if the DB is connected and migrated and therefore the instance is ready to accept traffic.
+
+Access the endpoint:
+
+```
+<your-instance-url>/healthz/readiness
+```
+
 
 ## metrics