api: add static router and improve path parser in rpc handler (#1437)

* api: add static router and improve path parser in rpc handler

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* expose metadata context key to be able to get unmodified map keys

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server/grpc: fix jsonpb codec for protobuf msg

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* api/handler/rpc: write 204 status code when rsp is nil

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* api/handler/rpc: add check for nil response for non javascript

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

codec.go

@@ -20,7 +20,11 @@ type bytesCodec struct{}
 type protoCodec struct{}
 type wrapCodec struct{ encoding.Codec }
 
-var jsonpbMarshaler = &jsonpb.Marshaler{}
+var jsonpbMarshaler = &jsonpb.Marshaler{
+	EnumsAsInts:  false,
+	EmitDefaults: false,
+	OrigName:     true,
+}
 
 var (
 	defaultGRPCCodecs = map[string]encoding.Codec{