[ENGINEERING] Set up firebase-admin

[yxli001]

What is the issue?

• Set up the firebase-admin package
  • For the service-account-key.json file, I would download it from the firebase dashboard and copy the contents of the entire file into a field in .env instead of importing it from directly from the JSON file (make sure to add it to env validation)
  • Feel free to reference these two files (auth.ts and firebase.ts) from my TSE project if you need help
• Create an auth middleware that checks for an authorization token in req.headers.authothorization in the format of Bearer [token] and decodes it into a user ID with firebase-admin's verifyIdToken auth function.
  • The decoded user ID should be put into req.userId so it can be used by the route handler
  • Use this middleware function, again, from my TSE project as reference. Note how it's being used in the user.ts route
• Once the user model is created, make a GET /api/user/whoami route - which should be protected by the auth middleware - that uses the user ID that was put in req.userId by the auth middleware to query a user that has this userId from MongoDB and return it with res.json()

NOTE: pay attention to how errors are handled/thrown back to the request sender in the TSE sample files

Additional context

• What is a middleware
• Authorization tokens
  • Just the first paragraph gives you a pretty good idea of what it is
• firebase-admin configuration
• Firebase docs about ID Tokens