Add support for repo access via Deploy Keys
Currently the Repo
abstraction has a url
field used to access the repository. This typically becomes something like https://host/owner/repo.git
or git@host:owner/repo.git
. In the latter case we could access the repository via a deploy key instead of with a user key. However, in order to do this we need to somehow tell ssh which identify file to use. This will always be done in combination with (perhaps manual) configuration both on the repo and on the bot deployment to generate and add the deploy keys. A given deploy key can only be used for one repository (at least on GitHub).