Document how to configure SSH setup without static credentials

I'm currently setting up a gitlab-runner with fleeting in Microsoft Azure and I'm having a hard-time since all examples/snippets that I can find use use_static_credentials = true. However, I would like to have a setup without static credentials and SSH. Can you please document how to set that up?

The approach I tried is to place the private and public keys for the SSH connection into /home/gitlab-runner/.ssh with chmod 0600 on the private key. The error I'm getting is ERROR: Preparation failed: preparing environment: dial ssh: after retrying 30 times: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none], no supported methods remain.

My connector config looks as follows:

[runners.autoscaler.connector_config]
use_static_credentials = false
timeout = "10m"
protocol = "ssh"
use_external_addr = false