add hint in find function

[chy373]

add hint in find function, so we can get result faster

another question: Why odmantic's model find function use motor's aggregate instead of find?

[art049]

Since there is not really the index support yet (#93), it's probably not the best time to add this feature. If you want to draft a PR, ofc it wouldn't be a problem :grinning:

Why odmantic's model find function use motor's aggregate instead of find?

The main benefit of using an agregation pipeline is to be able to get all the documents (even the referenced ones) in one single query.