cluster: add new config to restore original dst address from :authority header (#20534)

Signed-off-by: Yuchen Dai <silentdai@gmail.com>

Mirrored from https://github.com/envoyproxy/envoy @ 59d61d11ffb410ddbc5d0ced90795e0f7b279f0e

envoy/config/cluster/v3/cluster.proto

@@ -474,9 +474,8 @@ message Cluster {
     option (udpa.annotations.versioning).previous_message_type =
         "envoy.api.v2.Cluster.OriginalDstLbConfig";
 
-    // When true, :ref:`x-envoy-original-dst-host
-    // <config_http_conn_man_headers_x-envoy-original-dst-host>` can be used to override destination
-    // address.
+    // When true, a HTTP header can be used to override the original dst address. The default header is
+    // :ref:`x-envoy-original-dst-host <config_http_conn_man_headers_x-envoy-original-dst-host>`.
     //
     // .. attention::
     //
@@ -488,6 +487,10 @@ message Cluster {
     //
     //   If the header appears multiple times only the first value is used.
     bool use_http_header = 1;
+
+    // The http header to override destination address if :ref:`use_http_header <envoy_v3_api_field_config.cluster.v3.Cluster.OriginalDstLbConfig.use_http_header>`.
+    // is set to true. If the value is empty, :ref:`x-envoy-original-dst-host <config_http_conn_man_headers_x-envoy-original-dst-host>` will be used.
+    string http_header_name = 2;
   }
 
   // Common configuration for all load balancer implementations.