Allow SSH key selection for Repository Pull Mirroring

Description

Our organization currently has a very large number of repositories we have been manually mirroring from a customer's server for years. We just recently upgraded to Enterprise Starter, and we would like to use the built-in mirroring. However, the customer's server only uses SSH authentication. Creating over 200 new SSH public keys and pushing those keys to the customer's server would be very time consuming and not worth the effort.

Proposal

It would be beneficial to create either a group or admin SSH key that can be chosen for Repository Pull Mirroring. Something similar to how the Deploy Keys settings for a project would work.

Links / references