I am now a VMware -> XCP-ng convert and wish I had known sooner. This post helped me get to the point of fully automated template and server builds with Packer/Terraform.
Here are my code samples. Hope it helps someone else!
Packer/XCP-ng Templates
https://github.com/mtcoffee/xcp-ng-packer-examples
Terraform/XCP-ng Templates
https://github.com/mtcoffee/xcp-ng-terraform-examples