Fail to deploy charm with storage parameter

[dragomirp]

Description

Trying to update libjuju from 3.5.0.0 to 3.5.2.0 breaks tests setting the storage parameter during deploy. Example CI run can be seen here. Deploying a locally build charm with:

        await ops_test.model.deploy(
            charm,
            application_name=FIRST_APPLICATION,
            num_units=3,
            series=CHARM_SERIES,
            storage={"pgdata": {"pool": "lxd-btrfs", "size": 2048}},
            config={"profile": "testing"},
        )

Will result in:

  File "/home/runner/work/postgresql-operator/postgresql-operator/tests/integration/ha_tests/test_restore_cluster.py", line 40, in test_build_and_deploy
    await ops_test.model.deploy(
  File "/home/runner/work/postgresql-operator/postgresql-operator/.tox/integration/lib/python3.10/site-packages/juju/model.py", line 1841, in deploy
    return await self._deploy(
  File "/home/runner/work/postgresql-operator/postgresql-operator/.tox/integration/lib/python3.10/site-packages/juju/model.py", line 2154, in _deploy
    storage=***k: parse_storage_constraint(v) for k, v in (storage or dict()).items()***,
  File "/home/runner/work/postgresql-operator/postgresql-operator/.tox/integration/lib/python3.10/site-packages/juju/model.py", line 2154, in <dictcomp>
    storage=***k: parse_storage_constraint(v) for k, v in (storage or dict()).items()***,
  File "/home/runner/work/postgresql-operator/postgresql-operator/.tox/integration/lib/python3.10/site-packages/juju/constraints.py", line 131, in parse_storage_constraint
    for m in STORAGE.finditer(constraint):
TypeError: expected string or bytes-like object

Trying to deploy something like:

await model.deploy("postgresql", storage={"pgdata": "lxd-btrfs,1,2G"}, config={"profile": "testing"})

Fails different validation:

TypeError: juju.client._definitions.Constraints() argument after ** must be a mapping, not str

I think the issue is caused by the additional validation added in model.py L2119

Urgency

Annoying bug in our test suite

Python-libjuju version

3.5.2.0

Juju version

3.4.4

Reproduce / Test

>>> import asyncio
>>> from juju.model import Model
>>> model = Model()
>>> await model.connect_current()
>>> await model.deploy("postgresql", storage={"pgdata": {"pool": "lxd-btrfs", "size": 2048}}, config={"profile": "testing"})

[addyess]

@cderici -- i'm also affected by this

i tries switching to the new style of arguments:
using

storage = {
    "osd-devices": "8G,1",
    "osd-journals": "8G,1",
}

and that breaks when it tries parse these as client.Contraints in model.py

        if storage:
            storage = {
                k: client.Constraints(**v)
                for k, v in storage.items()
            }