Add S3-specific endpoint to generated AWS profile

[anisaoshafi]

Motivation

aws --profile localstack used directly (not through lstk's own proxies) sent S3 requests to the profile's general endpoint, breaking S3's virtual-host-style bucket addressing.

Solution

lstk setup aws now writes an S3 endpoint override in a [services localstack] block, referenced via services = localstack in the profile. It reuses the existing endpoint.S3Addressing helper already used by the Terraform/CDK proxies. This block follows the same idempotency and --force overwrite rules as the rest of the profile.

Review

Small, self-contained, covered by unit and integration tests. Self-merge candidate.

Closes DEVX-755

[joe4dev]

Good to see S3 compatibility addressed in the AWS profile. That's particularly important to cdk. I really like the non-destructive edit in ~/.aws/profile 👏 ✨

A couple of non-blocking questions/suggestions:

❓ Do we want to offer a fallback for customers being blocked by DNS rebind protection, similar to the probing we do in the LocalStack Toolkit https://github.com/localstack/localstack-toolkit-vscode/pull/51?

This block follows the same idempotency and --force overwrite rules as the rest of the profile.

❓ What is the intended behavior of --force?
Given an existing ~/.aws/profile, both non-force and --force performed a non-destructive edit. Does --force simply skip the interactive "[Y/n]" prompt?

nit: The confirmation message "✔︎ Created LocalStack profile in ~/.aws/config" does not distinguish between Create and Update.

Sidenotes

Not directly related, just FYI:

• The lstk aws proxy command does not respect the --profile localstack. Is this intentional or is there a workaround?
• The AWS VSCode Extension cannot parse the service-specific section and spams verbose logs (their bug):