ratelimit: support response_headers_to_add (#22593)

Signed-off-by: hejianpeng <hejianpeng2@huawei.com>

Mirrored from https://github.com/envoyproxy/envoy @ 8925f74675b6ced1b0205daf73766724e295a6cc

envoy/extensions/filters/http/ratelimit/v3/rate_limit.proto

@@ -2,6 +2,7 @@ syntax = "proto3";
 
 package envoy.extensions.filters.http.ratelimit.v3;
 
+import "envoy/config/core/v3/base.proto";
 import "envoy/config/core/v3/extension.proto";
 import "envoy/config/ratelimit/v3/rls.proto";
 import "envoy/config/route/v3/route_components.proto";
@@ -24,7 +25,7 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 // Rate limit :ref:`configuration overview <config_http_filters_rate_limit>`.
 // [#extension: envoy.filters.http.ratelimit]
 
-// [#next-free-field: 11]
+// [#next-free-field: 12]
 message RateLimit {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.config.filter.http.rate_limit.v2.RateLimit";
@@ -120,6 +121,11 @@ message RateLimit {
   // .. note::
   //   If this is set to < 400, 429 will be used instead.
   type.v3.HttpStatus rate_limited_status = 10;
+
+  // Specifies a list of HTTP headers that should be added to each response for requests that
+  // have been rate limited.
+  repeated config.core.v3.HeaderValueOption response_headers_to_add = 11
+      [(validate.rules).repeated = {max_items: 10}];
 }
 
 // Global rate limiting :ref:`architecture overview <arch_overview_global_rate_limit>`.