Impossible to query for _id using whereRaw

[galzetta]

• Laravel-mongodb Version: 3.2.3
• PHP Version: 7.3
• Database Driver & Version: Mongo DB 4.4, ext-mongo >= 1.9

Description:

Steps to reproduce

1. Try to query something using Class::query()->whereRaw(['_id' => 'some-value']) or Class::query()->whereRaw(['_id' => ['$eq' => 'some-value']])

Expected behaviour

The query should return exactly the same results as Class:query()->where('_id', 'some-value')

Actual behaviour

No result is returned

---

In my situation I have some subscriptions and some logic that defines general rules for when a customer can see a certain subscription type. However I also need to implement an override (basically customer service wants to specify that user X can see subscription type Y even though this doesn't follow the standard rules). To do this I want to write a query like:

->whereRaw([
    '$or' => [$set_of_standard_rules, ['_id' => ['$in' => $user_overrides]]]
])

However the _id part is never matched, even when using the basic query whereRaw(['_id' => 'some-value']) or whereRaw(['_id' => ['$eq' => 'some-value']]).