Investigate setting up a SAML demo box with terraform

Why

If we can demo Group-SAML on a machine we control we can get user feedback on changes sooner instead of waiting for changes to be merged.

What

• Use https://gitlab.com/gitlab-com/dev-resources/ to set up a machine
• Create demo branch and use MR manual pipeline to create an omnibus package.
• Find out if there is a preferred way to go from terraform machine to GitLab installation on a subdomain.
• Configure the instance ready for demoing to customers