Support service principal login

[micya]

I'd like to autoscale the number of unmanaged simulators (via Kubernetes). As part of that, I would like to be able to automatically use the new simulators for training. The only way I can see right now is to run bonsai simulator unmanaged connect, which requires authentication.

Feature request: service principal logins to authenticate the Bonsai CLI (because I can't possibly log in interactively every time)