public async Task <ActionResult> PostAsync([FromBody] GroupDTO dto)
        {
            try
            {
                if (!ModelState.IsValid)
                {
                    return(BadRequest(ModelState));
                }
                var group = await groupService.AddAndGetIdAsync(dto);

                if (group != null)
                {
                    return(Ok(group.Value));
                }
                return(BadRequest());
            }
            catch (Exception e)
            {
                return(BadRequest(e));
            }
        }