Use .ssh/config instead of ENV vars to store certificates

[akulisek]

Problem

Using ENV vars for storing deployment keys, in my opinion, is an approach that avoids standard practices and lacks clarity. Also, within the app itself (built on this pack) there are no traces of why we're doing this.

Suggested approach

As previousely discussed, this is a suggestion to use, in my view, a more appropriate and straightforward tooling for setting up multiple deployment keys.

Instead of storing them in ENV vars, I'd prefer adding them locally and bind them to specific subdomains for github repositories, for example:

Host repository1.github.com
  HostName github.com
  User git
  IdentityFile /home/johndoe/.ssh/github/repository1_github_deployment_key.id_rsa
  IdentitiesOnly yes

In any Rails application built on this pack we'd then have to update our Gemfile and set source for gems requiring access via these deployment keys.

Adding and maintaining an example .ssh/config showcasing setup for all gems requiring deployment keys access could then be used by anyone doing a fresh repo clone / setup on their machine.

I believe this greatly improves the readability, adds context behind the problem and almost self documents itself.