Allow model to deploy with track/list/branch

[yanksyoon]

Description

It would be cool if I could do
model.deploy(..., channel="latest/edge/test") to specify the channel until the branch.
Currently, juju deploy jenkins-k8s --channel=latest/edge/test [email protected] works. However, with pylibjuju, I am not able to specify the branch.

juju.errors.JujuError: channel is malformed and has too many components latest/edge/test

Urgency

Casually wishlisting

Code I'd Like to Run

`model.deploy(..., channel="latest/edge/test")`