public IHttpActionResult UpdateGroup(Guid groupId, UpdateGroupCommand command)
        {
            if (command == null)
            {
                throw new ArgumentNullException("command");
            }
            if (groupId == Guid.Empty)
            {
                throw new ArgumentException("groupId must be defined.");
            }
            if (string.IsNullOrWhiteSpace(command.Name))
            {
                throw new ArgumentException("Group name must be defined.");
            }

            identityManagementService.UpdateGroup(groupId, command.Name, command.Description, command.IsDisabled, command.ExternalGroupName);
            return Ok();
        }