Bastion AMI upgrade information

We’ve been using several bastion clusters in the ECI AWS accounts for a long time. However, most clusters created via Terraform use the default AMI provided by the Terraform module. The default uses an AMI based on Ubuntu-14 which is not supported anymore according to Site infra Golden AMI document.

The recommended version going forward is to use a Bastion AMI based on Ubuntu-20. Here’s a reference PR. If you run into Terraform CD issues while merging this, just re-trigger CD using a new dummy PR.

Points to note