Prep for open source release

[edthedev]

Context

The TDX API tends to return the full name and email address of whoever is using it, and we record that network traffic into YAML files in GitHub to replay it while testing this app.

While these aren't incredibly sensitive, we kept this app private while we worked out how to reliably clean that information out of the network recording, as a courtesy to our team members.

That said, our network recording cleaner (vcr_cleaner Python library) is reliable now.

Again, as a courtesy, we should squash older commits before we publish.
But I think we are ready to share this source code, after that.

Tasks

• review our open-source checklist
• add our standard LICENSE, security.md, contributing, code of conduct files.
• add end-of-life language to the top of CHANGELOG
• make sure that key features from git log are documented in CHANGELOG
• squash the commit history to eliminate older versions of the YAML network traffic recordings
• unprotect the main branch
• force push the squashed history to main
• delete all other branches
• review the cassette files for any concerns
• re-protect the main branch #124
• re-run our detect-secrets tooling as an extra check #123
• review our default values in app.json, since they won't be valid for any other team #120
• find and remove any hard-coded translation tables that are unique to our environment #121
• publish this repository as open source #122

[edthedev]

Got the detect-secrets libraries added to our build, and then ran out of time. Will re-run our detection after the holiday, and then should be ready to publish.

[edthedev]

I've parted our the remaining work here into issues that are listed in #122. Closing this so that there's just that place to track.