feat: (IaC) include evidence field in json output [IAC-3161]

[sergiu-snyk]

Pull Request Submission Checklist

• Follows CONTRIBUTING guidelines
• Includes detailed description of changes
• Contains risk assessment (Low | Medium | High)
• Highlights breaking API changes (if applicable)
• Links to automated tests covering new functionality
• Includes manual testing instructions (if necessary)
• Updates relevant GitBook documentation (PR link: ___)

What does this PR do?

IaC custom rules may include evidence to why a certain policy passed for a resource. If that evidence (string) is specified, we display it in the JSON output for the rule.

Note: this applies only for custom IaC rules, since the standard rules are not required to provide this evidence, and were not modified to include it.

There should be no concerns about output size increase, IaC custom rules are used by a small fraction of the customers, and this field should be a one line string in the majority of cases, if at all added.

How should this be manually tested?

This functionality is fully covered by tests, so no need for a manual test, which is a bit complicated.
I write it here nevertheless, just in case.

1. A custom rule needs to be created and pushed to Snyk using snyk iac rules init. See an example here of what the rule could look like.The resources Rego rule declares a context, which needs to include an evidence string field.

2. Publish the rule bundle using snyk iac rules push.

3. Define a terraform file with a resource designed to pass the custom rule.

4. Run snyk iac test on the Terraform file, and expect to see the evidence message included in the relevant infrastructureAsCodeSuccesses entries.

What are the relevant tickets?

https://snyksec.atlassian.net/browse/IAC-3161

[PeterSchafer]

@sergiu-snyk please run npm run format to address the linter issues.

[sergiu-snyk]

@sergiu-snyk please run npm run format to address the linter issues.

I had run it originally, but then had some subsequent changes, for which I forgot and did not notice the failure because of the other issue. 🙏