Rust 使用 serde_json 进一步处理字段

我正在使用serde_json来解码来自GCP发布/订阅的推送消息.

#[derive(Debug, Deserialize, Serialize)]
pub struct PushMessage {
    pub message: Message,
    pub subscription: String,
}

在消息中，有效负载是data键下的Base64编码字符串:

#[derive(Debug, Deserialize, Serialize)]
pub struct Message {
    message_id: String,
    #[serde(with = "base64data")]
    pub data: String,
}

…我用一个简单的base64data模来解码:

// A serializer/deserializer for base64-encoded data
mod base64data {
    use serde::{Deserialize, Serialize};
    use serde::{Deserializer, Serializer};

    use base64::engine::general_purpose::STANDARD as base64;
    use base64::engine::Engine as _;

    pub fn serialize<S: Serializer>(v: &str, s: S) -> Result<S::Ok, S::Error> {
        let b64 = base64.encode(v);
        String::serialize(&b64, s)
    }

    pub fn deserialize<'de, D: Deserializer<'de>>(d: D) -> Result<String, D::Error> {
        let b64 = String::deserialize(d)?;
        base64
            .decode(&b64)
            .map(|v| String::from_utf8(v).expect("Invalid UTF-8"))
            .map_err(|e| serde::de::Error::custom(e))
    }
}

然而，我知道我期望接收的类型也被序列化为JSON(即，Base64编码的字符串解码为JSON字符串)，所以理想情况下，我想告诉serde_json继续处理该字段，而不仅仅是解码Base64数据.这可能吗(例如，通过为我们想要反序列化的类型传递一个泛型参数)？