http2: make nghttp2 less picky about field whitespace

In nghttp2 1.49.0 it returns error on leading and trailing whitespace in
header fields according to language in the recently shipped RFC 9113.

nghttp2 1.50.0 introduces an option to switch off this strict check and
this change enables this option by default which should make curl behave
more similar to how it did with nghttp2 1.48.0 and earlier.

We might want to consider making this an option in the future.

Closes #9448

lib/http2.c

@@ -1277,6 +1277,27 @@ void Curl_http2_done(struct Curl_easy *data, bool premature)
   }
 }
 
+static int client_new(struct connectdata *conn,
+                      nghttp2_session_callbacks *callbacks)
+{
+#if NGHTTP2_VERSION_NUM < 0x013200
+  /* before 1.50.0 */
+  return nghttp2_session_client_new(&conn->proto.httpc.h2, callbacks, conn);
+#else
+  nghttp2_option *o;
+  int rc = nghttp2_option_new(&o);
+  if(rc)
+    return rc;
+  /* turn off RFC 9113 leading and trailing white spaces validation against
+     HTTP field value. */
+  nghttp2_option_set_no_rfc9113_leading_and_trailing_ws_validation(o, 1);
+  rc = nghttp2_session_client_new2(&conn->proto.httpc.h2, callbacks, conn,
+                                   o);
+  nghttp2_option_del(o);
+  return rc;
+#endif
+}
+
 /*
  * Initialize nghttp2 for a Curl connection
  */
@@ -1317,7 +1338,7 @@ static CURLcode http2_init(struct Curl_easy *data, struct connectdata *conn)
     nghttp2_session_callbacks_set_error_callback(callbacks, error_callback);
 
     /* The nghttp2 session is not yet setup, do it */
-    rc = nghttp2_session_client_new(&conn->proto.httpc.h2, callbacks, conn);
+    rc = client_new(conn, callbacks);
 
     nghttp2_session_callbacks_del(callbacks);