feat: parse OS version from result of trivy-scan

[Nikkely]

What did you implement:

Currently, trivy-to-vuls don't parse OS version .
I made trivy-to-vuls parse it.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Add test case

Checklist:

You don't have to satisfy all of the following.

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Reference

• https://blog.github.com/2015-01-21-how-to-write-the-perfect-pull-request/

[kotakanbe]

LGTM

[MaineK00n]

How about rewriting it this way?

func setScanResultMeta(scanResult *models.ScanResult, report *types.Report) error {
	if report.Metadata.OS != nil {
		scanResult.Family = report.Metadata.OS.Family
		scanResult.Release = report.Metadata.OS.Name
		scanResult.ServerName = fmt.Sprintf("%s %s", scanResult.Family, scanResult.Release)
	} else {
		scanResult.Family = constant.ServerTypePseudo
		scanResult.ServerName = "library scan by trivy"
	}
	scanResult.ScannedAt = time.Now()
	scanResult.ScannedBy = "trivy"
	scanResult.ScannedVia = "trivy"

	if len(report.Results) == 0 {
		return xerrors.Errorf("scanned images or libraries are not supported by Trivy. see https://aquasecurity.github.io/trivy/dev/vulnerability/detection/os/, https://aquasecurity.github.io/trivy/dev/vulnerability/detection/language/")
	}

	// check vuls expected os or library
	for _, r := range report.Results {
		if !pkg.IsVulsExpectedOS(r.Type) && !pkg.IsVulsExpectedLib(r.Type) {
			return xerrors.Errorf("vuls not supported images or libraries. r.Type: %s", r.Type)
		}
	}
	return nil
}

[MaineK00n]

LGTM