Application.refresh() does not support passing new config options

[aieri]

Description

When using the juju CLI I can perform a charm refresh and config change in a single command. From the docs:

Charm settings may be added or updated at upgrade time by specifying the
--config option, pointing to a YAML-encoded application config file.

  juju refresh foo --config config.yaml

This is useful and sometimes even necessary (e.g. if the revision we are upgrading to has a new config option whose default we explicitly need to avoid using), but libjuju does not currently allow for the same behavior.
See

python-libjuju/juju/application.py

Line 802 in d2c1cae

'config_settings': None,

Urgency

It would save from a weird workaround

Code I'd Like to Run

await app.upgrade_charm(
    channel=channel,
    force_series=force_series,
    force_units=force_units,
    path=path,
    revision=revision,
    switch=switch,
    config=new_config_dict,
)