Using exists validation rule for embedded models

[gmedaglia]

Is it possible to use the exists validation rule when using embedded models?

Let's say I have my Foo model which EmbedsMany Bar models. In my DB I have something like this:

{
    "_id": "...",
    "foo_attr": "val",
    "bars": [
        {
            "_id": "...",
            "bar_attr": "val"
        },
        // More bars...
    ]
}

Is there a way I could use Laravel's exists rule for validating a bar id? Maybe something like this?

'bar_id' => 'exists:foos.bars,_id'