Add for_each

[brikis98]

Description

This PR adds for_each and for_each_reference support to the dependency block of boilerplate. If you pass in a list to these attributes, instead of creating the dependency once, boilerpalte will loop over each item in the for_each list, and run the dependency once for each of those items. You can access the current item in the loop using __each__.

The main use case for this is to generate sub-folders and files dynamically: e.g., in https://github.com/gruntwork-io/prototypes/pull/361, I use this to generate environments (dev, stage, prod) dynamically, based on which environments the user asked for.

Bonus fix: remove Rho from CODEOWNERS; GitHub was showing an error about that.

TODOs

Read the Gruntwork contribution guidelines.

• [x] Update the docs.
• [x] Run the relevant tests successfully, including pre-commit checks.
• [x] Ensure any 3rd party code adheres with our license policy or delete this line if its not applicable.
• [x] Include release notes. If this PR is backward incompatible, include a migration guide.

Release Notes (draft)

Added / Removed / Updated [X].

Migration Guide

[brikis98]

OK, this is now ready for review. I added docs and examples; and by virtue of putting the examples and some test fixtures in the right folders, this also automatically adds tests.

[brikis98]

Hm, there seems to be some issue preventing me from merging. Might be related to: https://github.com/orgs/community/discussions/58535. The suggestion there is to close and re-open the PR... Let me try that.

[brikis98]

That... did not work. WTF.

[brikis98]

Grr, no time to deal with this, will temporarily disable branch protection and merge.