grpc-json: add support for ignoring unknown query parameters (#7691)

* grpc-json: add support for ignoring unknown query parameters

Current behavior is not to transcode a request that contains a query parameter
that cannot be mapped. In cases where there is a specific set of parameters to
ignore one can use ignored_query_parameters. If there is a proxy or client
adding query parameters that one cannot control this won't work and the
transcoder becomes useless. ignore_unknown_query_parameters solves this problem.

Risk Level: low to medium
Testing: Added a unit test for the transcoder.
Tested manually, locally.
Docs Changes:
Added field description in api/envoy/config/filter/http/transcoder/v2/transcoder.proto
Release Notes:

Signed-off-by: Neri Marschik <codesuki@users.noreply.github.com>

Mirrored from https://github.com/envoyproxy/envoy @ 6af53be976c79a2b51a3f55825b722b58686c8a0

envoy/config/filter/http/transcoder/v2/transcoder.proto

@@ -114,4 +114,10 @@ message GrpcJsonTranscoder {
   // The client could ``post`` a json body ``{"shelf": 1234}`` with the path of
   // ``/bookstore.Bookstore/GetShelfRequest`` to call ``GetShelfRequest``.
   bool auto_mapping = 7;
+
+  // Whether to ignore query parameters that cannot be mapped to a corresponding
+  // protobuf field. Use this if you cannot control the query parameters and do
+  // not know them beforehand. Otherwise use ``ignored_query_parameters``.
+  // Defaults to false.
+  bool ignore_unknown_query_parameters = 8;
 }