Add an 'How-To' section to the Review Apps doc

Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/development/testing_guide/review_apps.md

@@ -62,6 +62,41 @@ You can also manually start the `review-qa-all`: it runs the full QA suite.
 
 Note that both jobs first wait for the `review-deploy` job to be finished.
 
+## How to?
+
+### Find my Review App slug?
+
+1. Open the `review-deploy` job.
+1. Look for `Checking for previous deployment of review-*`.
+1. For instance for `Checking for previous deployment of review-qa-raise-e-12chm0`,
+  your Review App slug would be `review-qa-raise-e-12chm0` in this case.
+
+### Run a Rails console?
+
+1. [Filter Workloads by your Review App slug](https://console.cloud.google.com/kubernetes/workload?project=gitlab-review-apps)
+  , e.g. `review-29951-issu-id2qax`.
+1. Find and open the `task-runner` Deployment, e.g. `review-29951-issu-id2qax-task-runner`.
+1. Click on the Pod in the "Managed pods" section, e.g. `review-29951-issu-id2qax-task-runner-d5455cc8-2lsvz`.
+1. Click on the `KUBECTL` dropdown, then `Exec` -> `task-runner`.
+1. Replace `-c task-runner -- ls` with `-- /srv/gitlab/bin/rails c` from the
+  default command or
+  - Run `kubectl exec --namespace review-apps-ce -it review-29951-issu-id2qax-task-runner-d5455cc8-2lsvz -- /srv/gitlab/bin/rails c`
+    and
+  - Replace `review-apps-ce` with `review-apps-ee` if the Review App
+    is running EE, and
+  - Replace `review-29951-issu-id2qax-task-runner-d5455cc8-2lsvz`
+    with your Pod's name.
+
+### Dig into a Pod's logs?
+
+1. [Filter Workloads by your Review App slug](https://console.cloud.google.com/kubernetes/workload?project=gitlab-review-apps)
+  , e.g. `review-1979-1-mul-dnvlhv`.
+1. Find and open the `migrations` Deployment, e.g.
+  `review-1979-1-mul-dnvlhv-migrations.1`.
+1. Click on the Pod in the "Managed pods" section, e.g.
+  `review-1979-1-mul-dnvlhv-migrations.1-nqwtx`.
+1. Click on the `Container logs` link.
+
 ## Frequently Asked Questions
 
 **Isn't it too much to trigger CNG image builds on every test run? This creates