public void OnActionExecuting(ActionExecutingContext context)
        {
            foreach (var argument in context.ActionArguments.Values.Where(v => v is AddUserToChannelRequest))
            {
                AddUserToChannelRequest command = argument as AddUserToChannelRequest;

                _channelValidationService.RequireUserIsGroupMemberFromChannel(command.Username, command.ChannelId);
                _channelValidationService.RequireUserIsNotChannelMember(command.Username, command.ChannelId);
            }
        }
        public IActionResult AddUserToChannel(AddUserToChannelRequest command)
        {
            _channelUserService.AddUserToChannelByUsername(command.Username, command.ChannelId);

            return(NoContent());
        }