Add #[derive(FromRequestParts)] (#1305)

* Add missing leading double colon

* Separate handling of last element in FromRequest derive

* FromRequestParts derive

* fix it and add lots of tests

* docs

* changelog

* Update axum-macros/src/lib.rs

Co-authored-by: Jonas Platte <[email protected]>

Co-authored-by: David Pedersen <[email protected]>

axum-macros/tests/from_request/pass/empty_tuple_parts.rs

@@ -0,0 +1,12 @@
+use axum_macros::FromRequestParts;
+
+#[derive(FromRequestParts)]
+struct Extractor();
+
+fn assert_from_request()
+where
+    Extractor: axum::extract::FromRequestParts<(), Rejection = std::convert::Infallible>,
+{
+}
+
+fn main() {}