Turn ssh_keygen role into a specific role for git server key setups

[marcus-grant]

Trying to make the generic version of role/ssh_keygen ran into a ton of problems. Generating the key and passing it through a prompt in the terminal works but trying to add it to known hosts is a massive pain. Follow geerlingguys' guide. Basically he advocates either directly copying a key from local which has some potentially touch security implications but if you can SSH in in the first place it might be worth it. But ultimately I've been meaning to learn how to setup agent forwarding which he goes over there as well. Check it out and find out the best way to finally get the initial github keys onto a host so you can clone private repositories.