Always store state in an Arc (#1270)

* Add extension and state benchmarks

* wip

* Arc the state everywhere

* don't require `S: Clone`

* fix example

axum-extra/src/extract/cookie/mod.rs

@@ -91,7 +91,7 @@ pub struct CookieJar {
 impl<S, B> FromRequest<S, B> for CookieJar
 where
     B: Send,
-    S: Send,
+    S: Send + Sync,
 {
     type Rejection = Infallible;
 

axum-extra/src/extract/cookie/private.rs

@@ -90,7 +90,7 @@ impl<K> fmt::Debug for PrivateCookieJar<K> {
 impl<S, B, K> FromRequest<S, B> for PrivateCookieJar<K>
 where
     B: Send,
-    S: Send,
+    S: Send + Sync,
     K: FromRef<S> + Into<Key>,
 {
     type Rejection = Infallible;

axum-extra/src/extract/cookie/signed.rs

@@ -108,7 +108,7 @@ impl<K> fmt::Debug for SignedCookieJar<K> {
 impl<S, B, K> FromRequest<S, B> for SignedCookieJar<K>
 where
     B: Send,
-    S: Send,
+    S: Send + Sync,
     K: FromRef<S> + Into<Key>,
 {
     type Rejection = Infallible;