Add Snyk to CircleCI pipeline

[megg-pd]

Context

This PR will enable Snyk Open Source scans in CircleCI.

Changes Include:

1. Updating the CircleCI config.yml to add the Snyk orb, and adding a job to run that scan

Engineering Team Code Owners Should Test, Validate, and Merge

Please update as needed and merge these PRs when you feel comfortable to do so.
We are asking the teams that own each repository to carefully test and merge these changes so they can monitor for any resulting issues, as they are more familiar with the code and deploy process.

Checklist for Team Code Owners

• Ensure that all builds are successful.
• Check review for any comments/addendums from Security Engineer that might need to be manually addressed.
• Approve and MERGE the PR when ready!

Checklist for Security Engineer

• The Snyk WebUI has been reviewed to ensure the repo is showing up as expected
• The Snyk scan completes successfully

[megg-pd]

This link wasn't accurate anymore. Version 2.1 came out 6yrs ago.

[gschueler]

hmm, do we need to rebase on main? I see the PD git orb states its purpose is to prevent "unwanted merge checks from overwriting existing deployed code", but I don't think that applies here

[megg-pd]

We probably could. This was in the original template that SRE-Delivery worked with me on, but it's possible it's not relevant here. I'll take that out in the next iteration.

[megg-pd]

I have some other possible changes coming for the Snyk scan, so I'm just holding any more work on this PR until I've confirmed those changes.

[gschueler]

@megg-pd thanks, I'm doing some other changes to fix issues with the other actions

[gschueler]

@megg-pd will there be other changes to this PR?

[megg-pd]

@gschueler Apologies, this is ready to go now. The main change was changing the failure threshold to "high". We were looking into making another change where it only fails when there's an upgrade path for vulnerable dependencies, however this would then make snyk hide the license policy violation failures, so we couldn't implement that tweak.