Allow Repo Mirroring via SSH

Currently repo mirroring only works via HTTP/HTTPS/GIT URLS. A customer is requesting to allow mirroring via SSH.

ZD Ticket: https://gitlab.zendesk.com/agent/tickets/79486

There an an issue opened for it here: #98 (closed). It SP1 but I guess we haven't seen it because the milestone is set to %Backlog

closed