Use type vars for resource registration to return the same type

[tim-hutchinson]

ResourceRegistry.register() currently indicates that it returns one a type that is a subclass of res.NamespacedResource or res.GlobalResource. However, that leads type checkers to only be able to check against those definitions, losing all the type information defined on the subclass.

Example

from dataclasses import dataclass
from lightkube.codecs import resource_registry
from lightkube.core.resource import NamespacedResourceG

@dataclass
class ExampleClass(NamespacedResourceG):
	foo: str = 'bar'

# Currently, EC will have the type Type[Union[NamespacedResource, GlobalResource]], rather than ExampleClass
EC = resource_registry.register(ExampleClass)

ec = EC()
# Will show a type error for foo not being a defined attribute on either NamespacedResource or GlobalResource
ec.foo

This changes the register signature to use a TypeVar instead, to indicate that the type returned is the same type as the input

[gtsystem]

Hi, looks good. Can you also increase the patch version in setup.py?

[tim-hutchinson]

@gtsystem - Done

[gtsystem]

Fix available in v0.15.2