Transit at Schiphol, Covid rules

I am having trouble finding and understanding the Covid-rules regarding transiting at Schiphol. The relevant details would be:

  • Travel is from Wales (UK) to Germany
  • Traveller is a German citizen and UK resident
  • Traveller had their second shot over 14 days prior to travel
  • Evidence for the vaccination will be the vaccination letter issues by the NHS in Wales

Under these circumstances, is transiting in Schiphol permitted? Are there additional demands, ie a recent negative test?