Implement Terragrunt to simplify staging and production environments.

[bryan-robitaille]

We currently have an issue keeping two separate terraform repos as moving changes through staging to production is cumbersome and error prone.

Terragrunt will allow for the declaration of separate stand alone modules allowing for easy injection of variables that differ between the staging and production environment.

Requires complete refactoring of terraform code for extraction of modules and variables.

Project that have already gone this path:
Notifications
Covid Alert Metrics

[bryan-robitaille]

Moving to icebox as there is no current capacity to complete. Hoping to have Platform SRE team complete.

[bryan-robitaille]

For reference: branch with existing work on migration
https://github.com/cds-snc/forms-staging-terraform/tree/terragrunt

[patheard]

Going forward, the Terragrunt refactor will happen in this repo as follows:

1. Create new folders to holder Terragrunt configuration.
2. Use Scratch account to validate infrastructure can be created properly.
3. Migrate existing Staging/Production AWS resources to the new Terragrunt state files.

Related to cds-snc/platform-sre-security-support#47