fix marshal ptr in httpc (#1789)

* fix marshal ptr in httpc

* add more tests

* add more tests

* add more tests

* fix issue on options and optional both provided

core/mapping/marshaler.go

@@ -16,7 +16,13 @@ const (
 func Marshal(val interface{}) (map[string]map[string]interface{}, error) {
 	ret := make(map[string]map[string]interface{})
 	tp := reflect.TypeOf(val)
+	if tp.Kind() == reflect.Ptr {
+		tp = tp.Elem()
+	}
 	rv := reflect.ValueOf(val)
+	if rv.Kind() == reflect.Ptr {
+		rv = rv.Elem()
+	}
 
 	for i := 0; i < tp.NumField(); i++ {
 		field := tp.Field(i)
@@ -87,6 +93,10 @@ func validate(field reflect.StructField, value reflect.Value, opt *fieldOptions)
 		return nil
 	}
 
+	if opt.Optional && value.IsZero() {
+		return nil
+	}
+
 	if len(opt.Options) > 0 {
 		if err := validateOptions(value, opt); err != nil {
 			return err