Implement JSONObject put_class ClassVar

[lgarber-akamai]

📝 Description

This pull request implements a new put_class JSONObject ClassVar, which allows JSONObject classes to specify an alternate JSONObject class to use as the schema when serializing for PUT requests.

This prevents read-only fields under mutable substructs from being included in PUT request bodies.

✔️ How to Test

The following changes expected you have pulled down this PR locally and run make install.

Unit Testing

make test-unit

Manual Testing

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

from dataclasses import dataclass
from typing import Optional
from linode_api4 import JSONObject


@dataclass
class SubStructOptions(JSONObject):
    test1: Optional[str] = None


@dataclass
class SubStruct(JSONObject):
    put_class = SubStructOptions

    test1: str = ""
    test2: int = 0


substruct_value = SubStruct(test1="abc", test2=123)

print("is_put=False:", substruct_value._serialize())
print("is_put=True:", substruct_value._serialize(is_put=True))

2. Ensure the output matches the following:

is_put=False: {'test1': 'abc', 'test2': 123}
is_put=True: {'test1': 'abc'}

[yec-akamai]

Tested and works well on my end, nice work!

[ykim-akamai]

LGTM