add labels

api/main.proto

@@ -84,6 +84,7 @@ message Product {
   repeated Variant variants = 10;
   repeated Characteristic characteristics = 11;
   int64 category = 12;
+  repeated Label labels = 13;
 }
 
 message GroupedProduct {
@@ -107,6 +108,10 @@ message Characteristic {
   string value = 2;
 }
 
+message Label {
+  string name = 1;
+}
+
 message GetProductReq {
   int64 id = 1;
 }