public void Delete(int id)
{
var existingUser = _context.Users.SingleOrDefault(u => u.Id == id);
if (existingUser == null)
{
return;
}
var userDevices = _context.Devices.Where(d => d.UserId == id).ToList();
_context.RemoveRange(userDevices);
_context.Remove(existingUser);
_context.SaveChanges();
}