Document the API keys needed to develop

[chartgerink]

In reviewing #301, I noticed I cannot run npm run test because it requires a Resend API key.

As far as I know, this key is undocumented in the project and hence, makes it harder to setup the testing environment for developers. It might help to get an overview of these potential issues, and workarounds if relevant.

I ended up running vitest <file> instead, so it was not a blocker, but the Resend API key will be needed if somewhere in the deployment/testing process we want to be able to run npm run test.

Are there any other API keys that are critical?

[doomlab]

Alright @chartgerink - question - do we think we can move the tests for these two (login checks) to like production environment or something else? Basically, we wouldn't want to mandate this specific email setup as part of tests. Thoughts?

[chartgerink]

You could add the workaround to only run these tests if the relevant environment variables are necessary. This way they would work both in production and the staging area/dev deployment.