Terraform module structure

Modules should follow the Standard Module Structure from Terraform:

• README.md - Documentation for the module:
  • Intro and purpose
  • terraform-docs output (use <-- {BEGIN|END}_TF_DOCS --> fences)
  • Example usage
• versions.tf - Minimum Terraform and provider versions
• variables.tf - Variable inputs
• outputs.tf - Output definitions
• data.tf - Data sources
• locals.tf - Local variables
• Either:
  • main.tf - All the resources in a simple module
  • *.tf - Logical clusters of discrete "features" within a module

Unlike the Terraform documentation, we don't suggest creating a base set of files even if they're empty - just omit that file until it's needed.