Proposal: EnumMapAttribute

[jisaacstone]

Using a MapAttribute as a raw container that has Enum values does not work.

eg

class MyModel(Model):
    # this does not work as expected - errors on serialization
    my_enum_mapping = MapAttribute[str, MyEnum](null=False, default=dict)

My current workaround is to subclass and then override the methods:

class MyModel(MapAttribute[str, MyEnum]):
    @classmethod
    def is_raw(cls) -> bool:
        return True

    def serialize(
        self, values: "MyModel", *, null_check: bool = True
    ) -> dict[str, MyEnum]:
        container = {}
        for attr_name in values:
            v = values[attr_name]
            attr_class = UnicodeEnumAttribute(MyEnum)
            attr_type = attr_class.attr_type
            attr_value = attr_class.serialize(v)
            container[attr_name] = {attr_type: attr_value}
        return container

    def deserialize(
        self, values: "MyModel"
    ) -> dict[str, MyEnum]:
        return {
            k: UnicodeEnumAttribute(MyEnum).deserialize(attr_value)
            for k, v in values.items()
            for attr_type, attr_value in v.items()
        }

Would not be much work to turn this code into something generic and reusable - happy to do the work and contribute upstream if it is desired