SSH debugging allows a user to identify and resolve issues or errors that occur through the secure shell (SSH) connection between a client and a server.
To enhance the security of the runner and the infrastructure behind the runner, only user ssh-keys registered on Authorized Keys are allowed by default on tmate-ssh-server charm.
Authorized keys are registered via action-tmate's
limit-access-to-actor feature. This feature uses GitHub users's SSH key to launch an instance
of tmate session with -a option, which adds the user's SSH key to ~/.ssh/authorized_keys.