How to rename key of nested property

Hi Guys,

I’m trying to update a nested key in a document with no success, The example below is based in one that I found on the internet,

{
    "blog": "testblog1",
    "comment":  {
        "user_id": 883
    }
}

I want to rename user_id to customer_id, how can I do that?

Thanks in advance,

Jorge