Support custom config for dacite defaults in AvroModel

[billy-doyle]

Is your feature request related to a problem? Please describe.
Problem is I have a dataclass which has a Union of multiple similar but slightly different schemas. One such schema has all the fields from another, but the other has an additional field. By suppling the strict and strict unions match parameters I am able fix this.

Full reproducible example below:

from typing import Type, TypeVar, Union
from dataclasses import dataclass
from dacite import from_dict
from dataclasses_avroschema import AvroModel
from dataclasses_avroschema.types import JsonDict


@dataclass
class Foo(AvroModel):
    b: int

@dataclass
class Bar(AvroModel):
    a: str
    b: int


@dataclass
class Baz(AvroModel):
    action: Union[Foo, Bar]


data = {"a": "a", "b": 2}
bar = from_dict(Bar, data)
print(bar)
# Bar(a='a', b=2)

baz = Baz(bar)
print(baz)
# Baz(action=Bar(a='a', b=2))

serialized_val = Baz(bar).serialize()

print(Baz.deserialize(serialized_val, create_instance=False))
# {'action': {'a': 'a', 'b': 2}}
print(Baz.deserialize(serialized_val))
# Baz(action=Foo(b=2)) # INCORRECT!



CT = TypeVar("CT", bound="AvroModel")

class CustomAvroModel(AvroModel):
    # https://github.com/marcosschroh/dataclasses-avroschema/blob/2a100666c93afb3f4916ea84b2ed9904b71a3632/dataclasses_avroschema/schema_generator.py#L206

    @classmethod
    def config(cls: Type[CT]) -> JsonDict:
        """
        Get the default config for dacite and always include the self reference
        """
        # We need to make sure that the `avro schemas` has been generated, otherwise cls.klass is empty
        # It won't affect the performance because the rendered schema will be store in cls.rendered_schema
        if cls.klass is None:
            # Generate dataclass and metadata
            cls.klass = cls.generate_dataclass()

        return {
            "check_types": False,
            "forward_references": {
                cls.klass.__name__: cls.klass,
            },
            "strict_unions_match": True,
            "strict": True,
        }


@dataclass
class Baz(CustomAvroModel):
    action: Union[Foo, Bar]


baz = Baz(bar)
serialized_val = Baz(bar).serialize()
print(Baz.deserialize(serialized_val))
# Baz(action=Bar(a='a', b=2)) # CORRECT!

Describe the solution you'd like
I would like a simpler way to specify the dacite defaults passed to the config method. I am not sure the best way to handle this, however maybe something like the following would be better?:

@dataclass
class Baz(AvroModel):
    action: Union[Foo, Bar]

    class DaciteConfig:
        strict = True
        strict_unions_match = True

Describe alternatives you've considered
Alternative is to have the CustomAvroModel as currently shown in the reproducible example. This could likely be abstracted better.

Additional context
No additional context.

[marcosschroh]

Hi @billy-doyle

I think we can add this functionality to the class Meta. I will create a PR

[billy-doyle]

I had considered putting it in the Meta class but wasn't sure if it was the proper place or not. Sounds good to me though!