add ability to unmarshal to structpb.Value

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

urlencode.go

@@ -1,12 +1,14 @@
 // Package urlencode provides a urlencode codec
-package urlencode // import "go.unistack.org/micro-codec-urlencode/v3"
+package urlencode
 
 import (
+	"encoding/json"
 	"io"
 
 	pb "go.unistack.org/micro-proto/v3/codec"
 	"go.unistack.org/micro/v3/codec"
 	rutil "go.unistack.org/micro/v3/util/reflect"
+	"google.golang.org/protobuf/types/known/structpb"
 )
 
 type urlencodeCodec struct {
@@ -75,6 +77,16 @@ func (c *urlencodeCodec) Unmarshal(b []byte, v interface{}, opts ...codec.Option
 		return err
 	}
 
+	switch t := v.(type) {
+	case *structpb.Value:
+
+		buf, err := json.Marshal(mp)
+		if err == nil {
+			err = t.UnmarshalJSON(buf)
+		}
+		return err
+	}
+
 	return rutil.Merge(v, rutil.FlattenMap(mp), rutil.Tags([]string{"protobuf", "json", "xml", "yaml"}), rutil.SliceAppend(true))
 }