public void AddMember(GroupMemberViewModel viewModel)
{
string userRole = _groupMemberRepository.GetRole(viewModel.GroupId, viewModel.CurrentUserId);
if (userRole.Equals(RoleNames.ROLE_OWNER) &&
!_groupMemberRepository.IsInGroup(viewModel.GroupId, viewModel.UserId))
{
var entity = viewModel.ToEntity();
entity.JoinedAt = DateTime.Now;
_groupMemberRepository.AddUserToGroup(entity);
}
else
{
throw new ArgumentException("User is already in this group.");
}
}