feat(go): implement transformation of module into a model

[ewanharris]

Description

Implements transformModuleFilesToModel for the Go package, this is based on the JS implementation in #178 so please refer to that PR for some context.

This branch is based on the one for #178 so is draft for now, will rebase once that has been merged.

References

Go portion of #153

Review Checklist

• [x] I have clicked on "allow edits by maintainers".
• [ ] I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• [x] The correct base branch is being used, if not main
• [ ] I have added tests to validate that the change in functionality is working as expected