Compute resources key pair workflow

[dLobatog]

The way some compute resources (Openstack, EC2...) create a key pair is currently very obscure for the user. The process should be documented, especially since it stores the secret key on the database and it's not retrievable in any way by any user other than people with access to the Foreman database.

[stbenjam]

👍

I need to fix up theforeman/community-templates#93 as a generic user data for everything, but that takes an SSH key param and deploys it with cloud init. If we make similar changes to the finish script it would make it more useable...