feat!: Refactor to use latest modules provided by terraform-aws-modules

[bryantbiggs]

Description

• Nearly all resources have been removed/replaced with the latest terraform-aws-modules equivalents
  • The VPC module has been removed entirely since most users will already have an existing VPC implementation
  • SSM parameters are no longer created within the module - handling secrets has been moved out of the module and left to users discretion
• Git provider specific implementation details have been removed from the root module. Users are able to pass the necessary Atlantis environment variables (or flags via container definition cmd) for the git provider of their choosing, as well as any other Atlantis settings they wish to utilize. Only the bare minimum Atlantis settings are provided in the module (Atlantis URL and port)
• Examples have been updated/replaced with two examples that demonstrate usage with GitHub in both a "complete" setup where the module creates nearly all resources required (save for the necessary integration bits, etc.), as well as a separated setup that demonstrates how users can utilize an existing ECS cluster and/or application load balancer (ALB)
• Doc examples have been updated and consolidated:
  • A supplemental doc section has been added that will be used to help demonstrate how users can integrate with other git providers such as GitLab and BitBucket, plus demonstrate common alternate configurations such as using a GitHub app for authenticated access
  • The ALB authenticated listener examples have been re-located to the ALB modules usage patterns docs. Since this module is really a wrapper around a collection of other modules the focus of the docs are really scoped to Atlantis specifics and any module level (think infrastructure level) changes are relegated to their respective module repository
• The GitHub and GitLab provider blocks have been removed from their respective webhook sub-modules. Its better to let users specify this so that they have full access to how they wish to configure the providers

Motivation and Context

• Resolves Task definition is broken with pre-created secrets #67
• Resolves Using an old version of terraform-aws-modules/ecs/aws #297
• Resolves feat: Support custom log configuration #342
• Resolves Not Deployable on Latest Provider #349
• Resolves create_route53_record=false still try to create a record for ACM #360
• Resolves fix: Add validate_certificate variable in atlantis module #361
• Resolves Expose /metrics endpoint through unauthenticated access #364

Breaking Changes

• Yes - due to the nature of Atlantis and the fact that it does not store any state, the recommended migration path is for users to de-provision their current implementation, and then re-provision using the updated syntax/configuration

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects
• I have executed pre-commit run -a on my pull request

[antonbabenko]

Looks very good!

[antonbabenko]

Maybe move these two additions to your global gitignore file?

[antonbabenko]

This PR is included in version 4.0.0 🎉

[github-actions]

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