Move FromRequest and IntoResponse into new axum-core crate (#564)

* Move `IntoResponse` to axum-core

* Move `FromRequest` to axum-core

* some clean up

* Remove hyper dependency from axum-core

* Fix docs reference

* Use default

* Update changelog

* Remove mention of default type

axum-core/src/extract/rejection.rs

@@ -0,0 +1,85 @@
+//! Rejection response types.
+
+define_rejection! {
+    #[status = INTERNAL_SERVER_ERROR]
+    #[body = "Cannot have two request body extractors for a single handler"]
+    /// Rejection type used if you try and extract the request body more than
+    /// once.
+    pub struct BodyAlreadyExtracted;
+}
+
+define_rejection! {
+    #[status = INTERNAL_SERVER_ERROR]
+    #[body = "Headers taken by other extractor"]
+    /// Rejection used if the headers has been taken by another extractor.
+    pub struct HeadersAlreadyExtracted;
+}
+
+define_rejection! {
+    #[status = INTERNAL_SERVER_ERROR]
+    #[body = "Extensions taken by other extractor"]
+    /// Rejection used if the request extension has been taken by another
+    /// extractor.
+    pub struct ExtensionsAlreadyExtracted;
+}
+
+define_rejection! {
+    #[status = BAD_REQUEST]
+    #[body = "Failed to buffer the request body"]
+    /// Rejection type for extractors that buffer the request body. Used if the
+    /// request body cannot be buffered due to an error.
+    pub struct FailedToBufferBody(Error);
+}
+
+define_rejection! {
+    #[status = BAD_REQUEST]
+    #[body = "Request body didn't contain valid UTF-8"]
+    /// Rejection type used when buffering the request into a [`String`] if the
+    /// body doesn't contain valid UTF-8.
+    pub struct InvalidUtf8(Error);
+}
+
+composite_rejection! {
+    /// Rejection used for [`Request<_>`].
+    ///
+    /// Contains one variant for each way the [`Request<_>`] extractor can fail.
+    ///
+    /// [`Request<_>`]: http::Request
+    pub enum RequestAlreadyExtracted {
+        BodyAlreadyExtracted,
+        HeadersAlreadyExtracted,
+        ExtensionsAlreadyExtracted,
+    }
+}
+
+composite_rejection! {
+    /// Rejection used for [`Bytes`](bytes::Bytes).
+    ///
+    /// Contains one variant for each way the [`Bytes`](bytes::Bytes) extractor
+    /// can fail.
+    pub enum BytesRejection {
+        BodyAlreadyExtracted,
+        FailedToBufferBody,
+    }
+}
+
+composite_rejection! {
+    /// Rejection used for [`String`].
+    ///
+    /// Contains one variant for each way the [`String`] extractor can fail.
+    pub enum StringRejection {
+        BodyAlreadyExtracted,
+        FailedToBufferBody,
+        InvalidUtf8,
+    }
+}
+
+composite_rejection! {
+    /// Rejection used for [`http::request::Parts`].
+    ///
+    /// Contains one variant for each way the [`http::request::Parts`] extractor can fail.
+    pub enum RequestPartsAlreadyExtracted {
+        HeadersAlreadyExtracted,
+        ExtensionsAlreadyExtracted,
+    }
+}