Return "To Be" Terraform State Data from validate-apply

Currently, the validate-apply API endpoint only returns a boolean success status.

Ideally, the API could return the changes that would be applied if the apply state was run based on the changes present in the Integration’s source, i.e., the output of the terraform plan comparing the current state to the changes.

It would be helpful for automation and CI/CD as external applications could see what changes were going to be applied without a user having to go into the web interface.