Convert `user.controller.js` to `async`/`await` syntax.

[lindapaiste]

Ref #521

Changes:

• Convert all user endpoint controllers to use async/await syntax.
• Got rid of async.waterfall() chaining.
• Rename function random to generateToken and make it aysnc.
• Make user method comparePassword be async, with a minor change to the passport.js file to support this.
• Changed 404 error messages from 'Document not found' to 'User not found'.

Limitations:

• I am using await mail.send(mailOptions); as this function returns a Promise, but the mail class doesn't handle errors correctly and will resolve instead of reject. I will fix this in an additional PR.
• I'm still unsure of the best way to handle unexpected errors from async functions. Some of these handlers have try/catch blocks, while others will throw the error and reject the promise. I basically kept the same amount of error handling on each function as was there before.
• Not every error is handled perfectly, but it's as good or better than before.
• Some of the code is very repetitive across handlers (particularly for sending emails). This can be cleaned up in the future.

I have verified that this pull request:

• [x] has no linting errors (npm run lint)
• [x] has no test errors (npm run test)
• [x] is from a uniquely-named feature branch and is up to date with the develop branch.
• [x] is descriptively named and links to an issue number, i.e. Fixes #123

[raclim]

Hi @lindapaiste! Just wanted to share some of the server logs I found during the days that peaked in errors. I noticed that during those times, the server would restart more frequently and that these two errors would show up mostly around those moments:

Error 1

Error 2

Based on the first image, I think it's coming from comparePassword in the user.js file? Or maybe from removing the return on line 51 in passport.js?

I also have a two more screenshots of other logs when the server restarts from two different days. I hope this was able to provide some context but let me know if you need more logs or other info here, thanks!!!

Log from 03/22/24

Log from 03/24/24