Revert "Revert "V0.4.0 imporve error response""

This reverts commit 9744f45e86.

backend/lib/validate_bridge/validator.go

@@ -0,0 +1,54 @@
+package validate_bridge
+
+import (
+	"reflect"
+	"sync"
+
+	"github.com/gin-gonic/gin/binding"
+	"gopkg.in/go-playground/validator.v9"
+)
+
+type DefaultValidator struct {
+	once     sync.Once
+	validate *validator.Validate
+}
+
+var _ binding.StructValidator = &DefaultValidator{validate: validator.New()}
+
+func (v *DefaultValidator) ValidateStruct(obj interface{}) error {
+	if kindOfData(obj) == reflect.Struct {
+
+		v.lazyinit()
+
+		if err := v.validate.Struct(obj); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (v *DefaultValidator) Engine() interface{} {
+	v.lazyinit()
+	return v.validate
+}
+
+func (v *DefaultValidator) lazyinit() {
+	v.once.Do(func() {
+		v.validate = validator.New()
+		v.validate.SetTagName("binding")
+
+		// add any custom validations etc. here
+	})
+}
+
+func kindOfData(data interface{}) reflect.Kind {
+
+	value := reflect.ValueOf(data)
+	valueType := value.Kind()
+
+	if valueType == reflect.Ptr {
+		valueType = value.Elem().Kind()
+	}
+	return valueType
+}