Usecase

I want to serialize a struct containing other structs to CSV, which is why I use flatten.
However some of these structs have fields with the same name, which make the output unpractical to read.
I would like to prefix the flattened fields to be able to distinguish them.

Minimal example

use serde::Serialize;

fn main() {
    let json = serde_json::to_string(&Message::default()).unwrap();
    println!("{}", json);
}

#[derive(Serialize, Default)]
struct Message {
    content: String,
    #[serde(flatten)] // put new feature here
    from: Person,
    #[serde(flatten)] // put new feature here
    to: Person,
}

#[derive(Serialize, Default)]
struct Person {
    name: String,
}

Output

{"content":"","name":"","name":""}

Wanted Output example

{"content":"","from.name":"","to.name":""}

Maybe this could be implemented as an option on the flatten macro, or as an extension on the renaming macro ?