Transform errors when extract parameters

[tisonkun]

Description of the feature

This code snippet:

#[handler]
async fn query(
    Json(query): Json<Query>,
) -> String {
    query.query
}

would be expanded to:

#[allow(non_camel_case_types)]
struct query;
impl poem::Endpoint for query {
    type Output = poem::Response;
    #[allow(unused_mut)]
    async fn call(&self, mut req: poem::Request) -> poem::Result<Self::Output> {
        let (req, mut body) = req.split();
        let p0 = <Json<Query> as poem::FromRequest>::from_request(&req, &mut body)
            .await?;
        async fn query(Json(query): Json<Query>) -> String {
            query.query
        }
        let res = query(p0).await;
        let res = poem::error::IntoResult::into_result(res);
        std::result::Result::map(res, poem::IntoResponse::into_response)
    }
}

I know I can change the return type of my function to customize error in my handling logic, but what if I'd like to decorate the error message when fail to <Json<Query> as poem::FromRequest>::from_request(&req, &mut body).await??.

Code example (if possible)

By default, it may return:

HTTP/1.1 400 Bad Request
Content-Length: 77
Connection: keep-alive
Date: Sun, 12 May 2024 06:30:37 GMT
Keep-Alive: timeout=4
Proxy-Connection: keep-alive

parse error: invalid type: integer `1`, expected a string at line 1 column 12

while I'd prefer to customize the error message, like:

HTTP/1.1 400 Bad Request
Content-Length: 77
Connection: keep-alive
Date: Sun, 12 May 2024 06:30:37 GMT
Keep-Alive: timeout=4
Proxy-Connection: keep-alive

0: fail to parse JSON payoad, at src/lib.rs:4:10
1: parse error: invalid type: integer `1`, expected a string at line 1 column 12