http_conn_manager: clarify hcm accesslog docs (#35611)

Signed-off-by: Boteng Yao <boteng@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ d283802bf8a26e4cb5f8ecdc07809f48a9464b7d

envoy/extensions/filters/network/http_connection_manager/v3/http_connection_manager.proto

@@ -589,26 +589,33 @@ message HttpConnectionManager {
   // emitted by the connection manager.
   repeated config.accesslog.v3.AccessLog access_log = 13;
 
+  // The interval to flush the above access logs.
+  //
   // .. attention::
-  // This field is deprecated in favor of
-  // :ref:`access_log_flush_interval
-  // <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.HcmAccessLogOptions.access_log_flush_interval>`.
-  // Note that if both this field and :ref:`access_log_flush_interval
-  // <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.HcmAccessLogOptions.access_log_flush_interval>`
-  // are specified, the former (deprecated field) is ignored.
+  //
+  //   This field is deprecated in favor of
+  //   :ref:`access_log_flush_interval
+  //   <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.HcmAccessLogOptions.access_log_flush_interval>`.
+  //   Note that if both this field and :ref:`access_log_flush_interval
+  //   <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.HcmAccessLogOptions.access_log_flush_interval>`
+  //   are specified, the former (deprecated field) is ignored.
   google.protobuf.Duration access_log_flush_interval = 54 [
     deprecated = true,
     (validate.rules).duration = {gte {nanos: 1000000}},
     (envoy.annotations.deprecated_at_minor_version) = "3.0"
   ];
 
+  // If set to true, HCM will flush an access log once when a new HTTP request is received, after the request
+  // headers have been evaluated, and before iterating through the HTTP filter chain.
+  //
   // .. attention::
-  // This field is deprecated in favor of
-  // :ref:`flush_access_log_on_new_request
-  // <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.HcmAccessLogOptions.flush_access_log_on_new_request>`.
-  // Note that if both this field and :ref:`flush_access_log_on_new_request
-  // <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.HcmAccessLogOptions.flush_access_log_on_new_request>`
-  // are specified, the former (deprecated field) is ignored.
+  //
+  //   This field is deprecated in favor of
+  //   :ref:`flush_access_log_on_new_request
+  //   <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.HcmAccessLogOptions.flush_access_log_on_new_request>`.
+  //   Note that if both this field and :ref:`flush_access_log_on_new_request
+  //   <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.HcmAccessLogOptions.flush_access_log_on_new_request>`
+  //   are specified, the former (deprecated field) is ignored.
   bool flush_access_log_on_new_request = 55
       [deprecated = true, (envoy.annotations.deprecated_at_minor_version) = "3.0"];