public async Task <IActionResult> SetUserTasksToStatusMailed(int userTaskId)
        {
            UserTask userTask = await userTaskService.FindAsync(userTaskId);

            if (userTask == null)
            {
                ProblemDetails problem = new ProblemDetails
                {
                    Title    = "User task was not found.",
                    Detail   = "User task with this ID does not exist.",
                    Instance = "CA523709-D2CB-4EC5-BE31-32758D2587D0"
                };
                return(NotFound(problem));
            }

            userTask.Status = UserTaskStatus.Mailed;
            userTaskService.Update(userTask);
            userTaskService.Save();

            return(Ok());
        }