Allow custom deployment scripts for Terraform steps
Currently it it not possible to script additional actions when planning to apply or applying a Terraform template. This means that additional steps are required to carry out simple takes like importing an exiting resource before planning, or uploading a saved plan to S3 so that it can be pulled and applied.
Many other steps have this configurable feature, and I believe it would be highly effective here.
- Pre-deployment script runs before 'terraform init' (allowing download of plan from S3, for example).
- Deployment script runs after 'terraform init' (allowing 'terraform import' after the template has been initialised, for example).
- Post-deployment script runs after 'terraform plan|apply' (allowing upload of plan to S3, for example).