public async Task <List <string> > All([FromHeader] string auth)
        {
            string user;

            if ((user = JwtBuilder.UserJwtToken(auth).Result) == null || !UserStore.Exists(user).Result)
            {
                HttpContext.Response.StatusCode = (int)HttpStatusCode.Unauthorized;
                return(null);
            }

            HttpContext.Response.Headers.Add("auth", auth);
            return(await ProductStore.Categories());
        }