Handle Multiple Stacks

[skorfmann]

This will change the commands synth, diff, deploy and destroy to handle more than one stack per application.

Current Behaviour prior to this Change

When using cdktf the application code is synthesized into the configured output folder (cdktf.out by default) as cdk.tf.json file. The output folder serves as working directory for the Terraform CLI for the commands which interacting with it (diff, deploy, destroy). Since we do have a static output folder, users might copy assets such as zip files as part of the stack synth manually in the output folder.

Changed behaviour

We'll have a stacks folder within the app output directory (cdktf.out), where each stack will synthesize itself in a sub directory (e.g. cdktf.out/stacks/stack-a). This will then serve as the working directory for all Terraform CLI commands. There won't be an automatic cleanup of the stacks directory.

Planned Changes

• Synth all stacks at once
• Synth a single stack only (useful when dealing with stacks which process large assets)
• Adapt deploy, diff, destroy to take a positional stack argument. If more than one stack exists, that's a mandatory argument
• Add a list stacks command
• Make sure the Terraform Cloud remote exec workflow doesn't break. This won't manage the Terraform workspaces on behalf of the user and therefore expects the workspaces to be present.
• Find a good way to access the stack's working directory on a construct level (e.g. to copy / generate assets) (extracted in Asset Construct #648)
• Add / change documentation for stacks. Point out, that we don't support automatic cross-stack references at this point
• Make sure local workflows handle the state files correctly
• Add check for existing terraform.tfstate file in project root and prompt the user to rename it

Fixes #289 #35

[skorfmann]

• Find a good way to access the stack's working directory on a construct level (e.g. to copy / generate assets)

This is possible in the current state, but not really convenient. Will create a follow up issue to make this more idiomatic.

[ansgarm]

Maybe we should also update the help file in our templates to contain the (sometimes optional) stack argument for some commands?

[ansgarm]

Just tested it locally, works great 🚀

[github-actions]

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