fix(rustproxy-http): improve async static file serving, websocket handshake buffering, and shared metric metadata handling

rust/crates/rustproxy-http/src/counting_body.rs

@@ -25,8 +25,8 @@ const BYTE_FLUSH_THRESHOLD: u64 = 65_536;
 pub struct CountingBody<B> {
     inner: Pin<Box<B>>,
     metrics: Arc<MetricsCollector>,
-    route_id: Option<String>,
-    source_ip: Option<String>,
+    route_id: Option<Arc<str>>,
+    source_ip: Option<Arc<str>>,
     /// Whether we count bytes as "in" (request body) or "out" (response body).
     direction: Direction,
     /// Accumulated bytes not yet flushed to the metrics collector.
@@ -56,8 +56,8 @@ impl<B> CountingBody<B> {
     pub fn new(
         inner: B,
         metrics: Arc<MetricsCollector>,
-        route_id: Option<String>,
-        source_ip: Option<String>,
+        route_id: Option<Arc<str>>,
+        source_ip: Option<Arc<str>>,
         direction: Direction,
     ) -> Self {
         Self {