Casting to SchemaField via output_field=

[michallowasrzechonek-silvair]

Hi,

First of all, thanks for this package ❤️

I think there is a small bit of functionality missing - it doesn't seem supported to access annotations generated on the database side as schema fields, like so:

class Foo(pydantic.BaseModel):
    foo: int


Model.objects.annotate(foo=JSONBuildObject(Value('bar'), Value(42)), output_field=SchemaField(Foo))))

this returns a plain JSON instead of an instance of Foo.

I think the fix would be a trivial one:

class PydanticSchemaField(...):
    def from_db_value(self, *args, **kwargs):
        value = super().from_db_value(*args, **kwargs)
        return self.to_python(value)