Add guideline to redeploy review app from a clean slate

.gitlab/ci/review-apps/main.gitlab-ci.yml

@@ -101,6 +101,7 @@ review-stop:
   extends:
     - .review-stop-base
     - .review:rules:review-stop
-  stage: post-qa
+  stage: deploy
+  needs: []
   script:
     - delete_k8s_release_namespace

doc/development/testing_guide/review_apps.md

@@ -37,6 +37,15 @@ browser performance testing using a
 
 ## How to
 
+### Redeploy Review App from a clean slate
+
+To reset Review App and redeploy from a clean slate, do the following:
+
+1. Run `review-stop` job.
+1. Re-deploy by running or retrying `review-deploy` job.
+
+Doing this will remove all existing data from a previously deployed Review App.
+
 ### Get access to the GCP Review Apps cluster
 
 You need to [open an access request (internal link)](https://gitlab.com/gitlab-com/access-requests/-/issues/new)
@@ -238,6 +247,16 @@ Leading indicators may be health check failures leading to restarts or majority
 The [Review Apps Overview dashboard](https://console.cloud.google.com/monitoring/classic/dashboards/6798952013815386466?project=gitlab-review-apps&timeDomain=1d)
 aids in identifying load spikes on the cluster, and if nodes are problematic or the entire cluster is trending towards unhealthy.
 
+### Database related errors in `review-deploy` or `review-qa-smoke`
+
+Occasionally the state of a Review App's database could diverge from the database schema. This could be caused by
+changes to migration files or schema, such as a migration being renamed or deleted. This typically manifest in migration errors such as:
+
+- migration job failing with a column that already exists
+- migration job failing with a column that does not exist
+
+To recover from this, please attempt to [redeploy Review App from a clean slate](#redeploy-review-app-from-a-clean-slate)
+
 ### Release failed with `ImagePullBackOff`
 
 **Potential cause:**