Support #[derive(FromRequest)] on enums (#1009)

* Support `#[from_request(via(...))]` on enums

* Check `#[from_request]` on variants

* check for non enum/struct and clean up

* changelog

* changelog

* remove needless feature

* changelog ref

axum-macros/tests/from_request/fail/enum_rejection_derive.rs

@@ -0,0 +1,7 @@
+use axum_macros::FromRequest;
+
+#[derive(FromRequest, Clone)]
+#[from_request(rejection_derive(!Error))]
+enum Extractor {}
+
+fn main() {}