More convenient models initialization

[Vitalium]

I want to suggest using decorators for simpler documents initialization.

class Registry:
    models: list = []

    def __call__(self, model: type[Document]):
        if model not in self.models:
            self.models.append(model)

        return model


register = Registry()


class Category(BaseModel):
    name: str
    description: str


@register
class Product(Document):
    name: str
    description: str = ''
    price: Indexed(Decimal)
    category: Category


@register
class Customer(Document):
    name: str
    type: str = 'User'


@register
class Order(Document):
    user: Link[Customer]
    products: list[Link[Product]] = []
    total: Decimal


client = AsyncIOMotorClient()
await init_beanie(database=client.test, document_models=register.models)

This is very useful when the amount of models is large enough.