refactor(NODE-5136): make authentication use async / await

[baileympearson]

Description

What is changing?

This PR cherry-picks unrelated refactors out of https://jira.mongodb.org/browse/NODE-3998. This is done to simplify review, as well as limit the surface area that I need to debug while looking for the issues in CI for https://jira.mongodb.org/browse/NODE-3998.

Is there new documentation needed for these changes?

No.

What is the motivation for this change?

Double check the following

• Ran npm run check:lint script
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket

[baileympearson]

what does initialize client return? you've removed the logic that checks for a null client after calling makeKerberosClient, which is only safe to do if initializeClient never resolves to null.

[nbbeeken]

The null checks are all to make typescript happy, TS did not handle the mutual exclusion of the two arguments passed to the callback. this function will throw if it doesn't return a client

[baileympearson]

Just because we've come this far, do you want to refactor up one more function?

const makeConnectionAsync = promisify(makeConnection);

async function connectAsync(..) {


}
export const connect = callbackify(connectAsync);

I don't think it makes sense to make makeConnection async, because ideally we'll refactor it eventually so it's not performing io at all (purely synchronous). It also currently handles event listeners on the socket, so just wrapping it in a promisify seems more straightforward.

With this last refactor, the auth module is basically completely refactored.

[nbbeeken]

I looked into making this change but it would only be usable here, the socks5 logic would need to be untangled from callbacks as well. Or we leave socks5 unchanged and it still uses the callback form at which point we haven't got much value out of making a promisified version. Let's stick with what we got so far

[baileympearson]

verbal approval because Github won't let me approve my own PR