Description

As opened before by @anderseknert in PR (#364)

• Trying to get rid of github.com/pkg/errors in OPA and use the stdlib errors instead. This was one of the upstream deps still using this library. If there's a reason for that, let me know 😅

The PR was stale, so I reopened a new one to be merge, as asked by @mangalaman93 .

Checklist

• Code compiles correctly and linting passes locally
• For all code changes, an entry added to the CHANGELOG.md file describing and linking to
  this PR