added body manipulation example for error handlers

actix-web/src/middleware/err_handlers.rs

@@ -50,6 +50,8 @@ type DefaultHandler<B> = Option<Rc<ErrorHandler<B>>>;
 /// will pass by unchanged by this middleware.
 ///
 /// # Examples
+/// ## Handler Response
+/// Header
 /// ```
 /// use actix_web::http::{header, StatusCode};
 /// use actix_web::middleware::{ErrorHandlerResponse, ErrorHandlers};
@@ -67,6 +69,25 @@ type DefaultHandler<B> = Option<Rc<ErrorHandler<B>>>;
 ///     .wrap(ErrorHandlers::new().handler(StatusCode::INTERNAL_SERVER_ERROR, add_error_header))
 ///     .service(web::resource("/").route(web::get().to(HttpResponse::InternalServerError)));
 /// ```
+///
+/// Body Content
+/// ```
+/// fn add_error_body<B>(res: dev::ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
+///    // Get the error message and status code
+///    let error_message = "An error occurred";
+///    // Destructures ServiceResponse into request and response components
+///    let (req, res) = res.into_parts();
+///    // Create a new response with the modified body
+///    let res = res.set_body(error_message).map_into_boxed_body();
+///    // Create a new ServiceResponse with the modified response
+///    let res = ServiceResponse::new(req, res).map_into_right_body();
+///    Ok(ErrorHandlerResponse::Response(res))
+///}
+///
+/// let app = App::new()
+///     .wrap(ErrorHandlers::new().handler(StatusCode::INTERNAL_SERVER_ERROR, add_error_body))
+///     .service(web::resource("/").route(web::get().to(HttpResponse::InternalServerError)));
+/// ```
 /// ## Registering default handler
 /// ```
 /// # use actix_web::http::{header, StatusCode};