chore: run the key server in dev backend

[sfoster1]

We can use mitmproxy to terminate tls! the best way is to run a second mitmproxy, like we run a second nginx, and feed it the certs generated by the key-server. We need a little stuff in the key-server to support this because mitmproxy wants the whole bundle of tls cert, tls key, and ca cert in a single PEM (one PEM can contain multiple entities) and then we can "notify" of configuration changes by touching the main mitmproxy script since it has hot module reload. Probably. Nobody's going to run their dev backend instance for 3 years anyway.

Closes EXEC-2524

Test Plan and Hands on Testing

• run dev-backend
• go to https://localhost:32313/health
• note that it works and you are using the flex certs! whee!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.27%. Comparing base (fd113e0) to head (2ad847e).
⚠️ Report is 1 commits behind head on edge.

Additional details and impacted files

@@           Coverage Diff           @@
##             edge   #21267   +/-   ##
=======================================
  Coverage   57.27%   57.27%           
=======================================
  Files        3991     3991           
  Lines      327280   327280           
  Branches    46563    46563           
=======================================
  Hits       187451   187451           
  Misses     139610   139610           
  Partials      219      219           

Flag	Coverage Δ
app	44.96% <ø> (ø)

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[SyntaxColoring]

Cool, thank you!