Add docs for securiy regression testing.

Author: James Page

tf/mysql-security-regression/README.md

@@ -0,0 +1,48 @@
+# Overview
+
+This terraform plan and helper scripts deploy a minimal OpenStack Service
+(Keystone) with MySQL Router and a 3 node MySQL InnoDB Cluster.
+
+The Security Proposed PPA is enabled by default, allowing basic regression
+testing of an OpenStack service against proposed security updates for the
+MySQL packages in Ubuntu.
+
+A workflow is provided to test supported Ubuntu LTS releases.
+
+# Setup
+
+Install required snaps:
+
+```
+./deps
+```
+
+# Terraform
+
+Use of the plan requires a previous bootstrapped Juju controller - works fine
+with LXD as no special kernel level features required.
+
+To apply the plan:
+
+```
+terraform init
+terraform apply -var ubuntu-base=ubuntu@24.04
+```
+
+and to teardown afterward:
+
+```
+terraform destroy
+```
+
+# Tempest
+
+Once the applications have deployed and configuration has completed, Tempest
+can be used to validate the deployment:
+
+```
+./tempest-run
+```
+
+This will run a smoke test of the Keystone service.
+