Use Fastify

[lxghtless]

Description:

Since Fastify seems to support all the settings we need to make this work with isomorphic servers, this PR switches to leveraging it. Lot's a big wins for Fastify plugins like:

• fastify-http-proxy
  • this gives us lots of wins, but a notable one is basic WS support.
• fastify-secure-session
  • this moves us away from needing a session store at all as it strongly encrypts the session as the cookie for "stateless sessions"

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• I have added appropriate tests and all tests pass

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