message: use postRequest in create method in base backend service
diff: @@ -37,19 +37,15 @@ export abstract class BaseBackendService<M extends BaseModel> {
  public create(params?: {}): Promise<M> {
  const command = 'create';
  let entity = this.entity.toLowerCase();
  - return this.http.post(BACKEND_API_URL, this.buildParams(command, params))
  - .toPromise()
  - .then((res: Response) => {
  - const response = res.json()[`${command}${entity}response`];
  + return this.postRequest(command, params)
  + .then(res => {
  + const response = res[`${command}${entity}response`];
  +
  if (entity === 'tag') {
  return response;
  }
  return this.prepareModel(response[entity]);
  - })
  - .catch(error => {
  - this.error.next(error);
  - return Promise.reject(error);
  });
  }
  