Include a script for authorized_keys lookup in the database
Per omnibus-gitlab#2855 (closed)
Currently, https://docs.gitlab.com/ee/administration/operations/speed_up_ssh.html asks users to create an unmanaged executable script in a custom location to enable authorized_keys database lookup, which isn't great.
The custom script just wraps a gitlab-shell script. We should add another gitlab-shell script that implements all of this, and in omnibus, ensure it's installed in the right place, with the right permissions.