[serde] Extend serde with custom macros?


Is it possible to extend serde with custom attributes?
I want to deserialize json into a struct like struct Root { id: u32 }, so id will always be u32.
But sometimes I get { "id": "42" } instead of { "id": 42 }. For now I’ve solved this problem with serde’s deserialize_with and a custom function. But since I want to learn more about macros I would like to write

#[derive(Debug, Deserialize)]
struct Root {
    id: u32

Is that possible? :confused: