refactor: remove serializeGroup method

AFFECTS PACKAGES:
@esri/arcgis-rest-groups

BREAKING CHANGE:
remove serializeGroup helper method from groups package

packages/arcgis-rest-groups/src/helpers.ts

@@ -1,26 +1,8 @@
-/* Copyright (c) 2017-2018 Environmental Systems Research Institute, Inc.
+/* Copyright (c) 2017-2019 Environmental Systems Research Institute, Inc.
  * Apache-2.0 */
 
 import { IUserRequestOptions } from "@esri/arcgis-rest-auth";
 
-import { IItemUpdate, IGroupAdd, IGroup } from "@esri/arcgis-rest-common-types";
-
 export interface IGroupIdRequestOptions extends IUserRequestOptions {
   id: string;
 }
-
-/**
- * (Deprecated) Serialize a group into a json format accepted by the Portal API
- * for create and update operations.
- *
- * @param group IGroup to be serialized
- * @returns a formatted JSON object to be sent to Portal
- * @private
- */
-/* istanbul ignore next */
-export function serializeGroup(group: IGroupAdd | IItemUpdate | IGroup): any {
-  const clone = JSON.parse(JSON.stringify(group));
-  const { tags = [] } = group;
-  clone.tags = tags.join(", ");
-  return clone;
-}