Entities semplification

* Entities semplification WIP

* Bug fixes after entity semplification

* Fix object serialization

cypress/fixtures/Entity1.js

@@ -5,15 +5,15 @@ export default class Entity1 extends IEntity {
     static attributes = {
         a: {
             type: Number,
+            default: 8,
         },
         b: {
             type: Number,
+            default: 9,
         },
     }
 
     constructor(values = {}) {
-        values.a ??= 8
-        values.b ??= 9
         super(values)
     }
 }