Add support for JAAS authentication flows

[jsimpso]

Description

Currently I'm unable to authenticate to a JAAS controller using pylibjuju, as JAAS doesn't support authenticating with username/password or macaroons. It would be great if we could use Oauth2 client credentials here to talk to JAAS, similarly to the Juju Terraform provider

Urgency

It would save from a weird workaround

Code I'd Like to Run

controller = Controller()
await controller.connect(
    endpoint='jaas.example.com',
    client_id='3c80d136-0115-4ba4-880f-a6158f419d7c',
    client_secret='a0e5fb1e-434d-4007-994d-c56673a34cd3',
    cacert=None,
)

[dimaqq]

Out of curiosity, would your use case be covered by Jubilant or Juju CLI?

[ale8k]

Out of curiosity, would your use case be covered by Jubilant or Juju CLI?

Juju CLI doesn't allow client credential login right now, just the Terraform provider. But it will cover this once this merges. Just waiting on a review from another team member.