feat: ✨ Add support for `assume-role` block in S3 backend for Terraform

[erikpaasonen]

Proposed changes

Adds support for the assume_role = {} block that is the current syntax for assuming a role for an S3 backend in Terraform.

Issues for these changes

#73

Types of changes

• [ ] Bugfix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (changes to code, which do not change application behavior)

Checklist

• [x] I have filled out this PR template
• [x] I have read the CONTRIBUTING doc
• [x] I have added automated tests that prove my fix is effective or that my feature works
• [x] I have added necessary documentation (README.md, CHANGELOG.md, etc. - if appropriate)

Dependencies and Blockers

Relevant Links

Further comments

Note: this will break compatibility with Terraform v1.1 and below. (The assume-role block was added in v1.2.) For reference, the current version of Terraform is 1.9.

[CLAassistant]

All committers have signed the CLA.

[erikpaasonen]

All tests passing locally for me.

[erikpaasonen]

I'm not entirely certain the test feedback was fully addressed before this was merged. could use follow-up if someone runs into an issue with this. 👍