Add status and body_text methods to built-in rejections (#1612)

* Add `status` and `body_text` methods to built-in rejections

This should make it easier to customize a built-in rejection while
preserving either the status or body.

Fixes https://github.com/tokio-rs/axum/issues/1611

* changelog

axum-core/src/macros.rs

@@ -19,12 +19,21 @@ macro_rules! define_rejection {
             }
         }
 
+        impl $name {
+            /// Get the response body text used for this rejection.
+            pub fn body_text(&self) -> String {
+                format!(concat!($body, ": {}"), self.0).into()
+            }
+
+            /// Get the status code used for this rejection.
+            pub fn status(&self) -> http::StatusCode {
+                http::StatusCode::$status
+            }
+        }
+
         impl crate::response::IntoResponse for $name {
             fn into_response(self) -> $crate::response::Response {
-                (
-                    http::StatusCode::$status,
-                    format!(concat!($body, ": {}"), self.0)
-                ).into_response()
+                (self.status(), self.body_text()).into_response()
             }
         }
 
@@ -70,6 +79,26 @@ macro_rules! composite_rejection {
             }
         }
 
+        impl $name {
+            /// Get the response body text used for this rejection.
+            pub fn body_text(&self) -> String {
+                match self {
+                    $(
+                        Self::$variant(inner) => inner.body_text(),
+                    )+
+                }
+            }
+
+            /// Get the status code used for this rejection.
+            pub fn status(&self) -> http::StatusCode {
+                match self {
+                    $(
+                        Self::$variant(inner) => inner.status(),
+                    )+
+                }
+            }
+        }
+
         $(
             impl From<$variant> for $name {
                 fn from(inner: $variant) -> Self {