mongo_proxy: support configurable command list for metrics (#13494)

Signed-off-by: David Bartley <bartle@stripe.com>

Mirrored from https://github.com/envoyproxy/envoy @ 78578736a7d6a17cd1da3312a38e6c229e7f6523

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

@@ -17,6 +17,7 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 // MongoDB :ref:`configuration overview <config_network_filters_mongo_proxy>`.
 // [#extension: envoy.filters.network.mongo_proxy]
 
+// [#next-free-field: 6]
 message MongoProxy {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.config.filter.network.mongo_proxy.v2.MongoProxy";
@@ -39,4 +40,9 @@ message MongoProxy {
   // Flag to specify whether :ref:`dynamic metadata
   // <config_network_filters_mongo_proxy_dynamic_metadata>` should be emitted. Defaults to false.
   bool emit_dynamic_metadata = 4;
+
+  // List of commands to emit metrics for. Defaults to "delete", "insert", and "update".
+  // Note that metrics will not be emitted for "find" commands, since those are considered
+  // queries, and metrics for those are emitted under a dedicated "query" namespace.
+  repeated string commands = 5;
 }