Add Keycloak pre-Stop hook

[slaskawi]

Summary

When performing Keycloak load testing, it turned out the Keycloak Kubernetes Service emits occasional HTTP 503 even if there is enough Pods to serve the traffic.

This thread highlights that this might be a manifestation of the Kubernetes Proxy design choices and adding a pre-Stop hook might solve it.

After performing some testing, indeed we can see the improvement.

Implementation details:

1. Add the pre-stop hook to the Keycloak StatefulSet:

154         lifecycle:
155           preStop:
156             exec:
157               command:
158               - /usr/bin/bash
159               - -c
160               - sleep 1

2. Ensure that it works by invoking:

• [Terminal 1] siege -l siege.log https://sso.uds.dev
• [Terminal 2] kubectl rollout restart statefulset -n keycloak keycloak

Aim at 100% availability

[slaskawi]

An upstream fix for HTTP 503s have been integrated, see quarkusio/quarkus#50625