Fix array for _id in find with $in not being converted to ObjectId.

[brianvanburken]

A query to find documents by _id does not work. An example of this query is:

const documents = await Model.find({ _id: { 
  $in: [ '576920dcde4ff8858d61efab', '576920dcde4ff8858d61efac' ] 
} } );¬

The whole parsing logic is skipped while using a query like { _id: '576920dcde4ff8858d61efab' } gets parsed.

[coveralls]

Changes Unknown when pulling 5596a37 on brianvanburken:fix-id-to-objectid-logics into * on vdemedes:master*.

[brianvanburken]

@vdemedes could you look into this PR? This fixes a bug that has affected us here. We would love to see this fixed :).

[vadimdemedes]

Merged, thank you a lot! Sorry about such a late response.

[brianvanburken]

Awesome! Thank you so much! ❤️ 💚 💙 💛 💜