session_request: don't expose proto-headers, use std hashmap

wtransport-proto/src/headers.rs

@@ -86,6 +86,12 @@ where
     }
 }
 
+impl AsRef<HashMap<String, String>> for Headers {
+    fn as_ref(&self) -> &HashMap<String, String> {
+        &self.0
+    }
+}
+
 impl From<StreamId> for ls_qpack::StreamId {
     #[inline(always)]
     fn from(value: StreamId) -> Self {

wtransport/src/endpoint.rs

@@ -9,6 +9,7 @@ use crate::driver::Driver;
 use crate::error::ConnectingError;
 use crate::error::ConnectionError;
 use quinn::Endpoint as QuicEndpoint;
+use std::collections::HashMap;
 use std::future::Future;
 use std::marker::PhantomData;
 use std::net::SocketAddr;
@@ -311,9 +312,9 @@ impl SessionRequest {
         self.stream_session.request().user_agent()
     }
 
-    /// Returns the whole headers associated with the request.
-    pub fn headers(&self) -> &Headers {
-        self.stream_session.request().headers()
+    /// Returns all header fields associated with the request.
+    pub fn headers(&self) -> &HashMap<String, String> {
+        self.stream_session.request().headers().as_ref()
     }
 
     /// Accepts the client request and it establishes the WebTransport session.