According to my experience, Terraform supports the Kubernetes provider, but all the things in that provider are separate, such as deployment, pod, service and etc. It does not provide a way to load all the things from a configuration file.

So, to deploy from the configuration file, I recommend you put the kubectl apply -f config_file in the null_resource. And it's also simple to delete all the things that have deployed with multiple mull_resource, you just need to use the Terraform command terraform destroy, it will remove all the resources that deployed through the Terraform file.