add requiredColumns

Author: dblythy

src/Controllers/SchemaController.js

@@ -151,6 +151,7 @@ const defaultColumns: { [string]: SchemaFields } = Object.freeze({
 });
 
 const requiredColumns = Object.freeze({
+  _User: 'username',
   _Product: ['productIdentifier', 'icon', 'order', 'title', 'subtitle'],
   _Role: ['name', 'ACL'],
 });
@@ -1600,4 +1601,5 @@ export {
   convertSchemaToAdapterSchema,
   VolatileClassesSchemas,
   SchemaController,
+  requiredColumns,
 };

src/RestWrite.js

@@ -15,6 +15,7 @@ var ClientSDK = require('./ClientSDK');
 import RestQuery from './RestQuery';
 import _ from 'lodash';
 import logger from './logger';
+import { requiredColumns } from './Controllers/SchemaController';
 
 // query and data are both provided in REST API format. So data
 // types are encoded by plain old objects.
@@ -1665,14 +1666,11 @@ RestWrite.prototype._updateResponseWithData = function (response, data) {
       this.storage.fieldsChangedByTrigger.push(key);
     }
   }
-  const defaultMandatoryColumnsInResponse = Object.freeze({
-    _User: ['username'],
-  });
   const skipKeys = [
     'objectId',
     'createdAt',
     'updatedAt',
-    ...(defaultMandatoryColumnsInResponse[this.className] || []),
+    ...(requiredColumns[this.className] || []),
   ];
   for (const key in response) {
     if (skipKeys.includes(key)) {