feat(opa): Export downloadPolicyE function

[joshmyers]

Description

Export downloadPolicyE function

We're using conftest so the opa module is almost what we want, but not
quite. Instead we'd like to use this function in our tests to download
our conftest rego policies from a remote URL. In order to do that, this
needs to be an exported function.

TODOs

Read the Gruntwork contribution guidelines.

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

Release Notes (draft)

Export DownloadPolicyE function.

[joshmyers]

@yorinasub17 any chance of getting some 👀 on this PR? 🙇

[yorinasub17]

LGTM! Thanks for the contribution and apologize for the delay! I'll kick off a regression test and if it passes, we can merge this in.

[yorinasub17]

Regression build: https://app.circleci.com/pipelines/github/gruntwork-io/terratest/1067/workflows/23bd6482-6e8c-49ab-aba6-cc24c38b7841

[joshmyers]

Thank you @yorinasub17 - I get a 404 from that link.

[yorinasub17]

You'll be able to see it once you log into circleci using your github account.

[yorinasub17]

Build failed, but I have confirmed that the test failures are unrelated to this change, so we can move forward with this change. Thanks again for the contribution!

[joshmyers]

Great, thanks @yorinasub17. Yup the fail looked unrelated. Any ideas when a release could be cut?

nvm - done 🎉