Support collection name alias generator

[piercsi]

Python's standard for class names in PascalCase, but chances are the standard for collection names might be different (ours is lowercase)

This means for each collection you have to remember to add in the name on settings, e.g.

class MyCollection(Document)
    a: int

    class Settings:
        name = 'mycollection'

Would it be possible in, say, init_beanie() to specify a collection name alias generator similar to pydantic, e.g

await init_beanie(database=client.get_database(), document_models=[MyCollection], alias_generator=lower)