new: Add available field to AccountAvailability class - #395

📝 Description

This pull requests adds the new available field to the AccountAvailability class and adjusts the unit tests/fixtures accordingly.

✔️ How to Test

The following test steps assume you have pulled this PR locally and run make install.

Unit Testing

make testunit

Manual Testing

1. In a linode_api4 testing environment (e.g. dx-devenv), run the following:

import argparse
import os

from linode_api4 import LinodeClient, Instance

client = LinodeClient(
    os.getenv("LINODE_TOKEN"),
    base_url="https://.../v4beta",
    ca_path="..."
)

for avail in client.account.availabilities():
    print(f"{avail.region} - {avail.available}")

NOTE: Ensure the base_url kwarg is updated to point at the correct API environment.

2. Ensure all regions and their corresponding availabilities are printed to the console with no errors.