Make the HTTP client factory reuse the underlying client

This avoids duplicating clients, and makes it so that they all share the same connection pool.

crates/axum-utils/src/client_authorization.rs

@@ -191,8 +191,7 @@ async fn fetch_jwks(
         .unwrap();
 
     let mut client = http_client_factory
-        .client()
-        .await?
+        .client("client.fetch_jwks")
         .response_body_to_bytes()
         .json_response::<PublicJsonWebKeySet>();