Feat: support nested non-primitive types for TypedExtras

[farmery]

Features

Nested Attribute Mapping: Adds the ability to parse and include nested non primitive objects.

Example:

@RestApi()
abstract class TypedExtrasTest {
  @DummyTypedExtras(
    id: '1234',
    config: Config(
      date: '24-10-2024',
      type: 'analytics',
      shouldReplace: true,
      subConfig: {'date': '24-11-2025'},
    ),
  )
  @GET('path')
  Future<void> list();
}

[farmery]

Hi @trevorwang, Please can you review this change?

[trevorwang]

Thanks for the contribution