Thanks @douglasw0 and @bcsgh! Your responses on this thread perfectly illustrate the two sides of the debate on provisioners in Terraform.
We have correctly identified that your question @obones is outside of the intended scope of Terraform, and so any solution that uses Terraform to solve this problem will be more of a work-around than a solution. The ultimate costs of that work-around may be higher than implementing a script or tool to work in conjunction with Terraform to get the job done; you’ll have to make a pragmatic decision here.
Unfortunately I do not have a good example for how to get this done with Terraform alone. As an example of the tools-based approach, check out this great post: Blue/Green workspace layout - #4 by apparentlymart. I hope this helps spark a solution to your problem.