feat(auth): Restore write-emails-to-disk script

[LZoog]

Because:

• This script is sometimes useful for debugging emails and seeing true link output with UTM params etc.

This commit:

• Restores the script from the commit prior to a3c090, with one tweak on config import

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This script is noted in our ecosystem-platform docs here, I'm wondering if it was removed accidentally here? While we don't usually need it, sometimes it's useful for debugging, and I'd like to use it to help me debug why an EJS variable passing to Fluent in plain text isn't working. I'll just rebase on top of this temporarily to debug, but wanted to open this as well.

Looks like a test file for this was also removed that I could potentially restore here too, but when finding where this was removed I saw another comment where it was unexpectedly failing so if this is just a tool we use once a year to help with something then I don't know if we need it running in CI on every PR.

[LZoog]

I'm going to go ahead and merge this without the tests since it's a debug tool that we only need rarely and I saw at least one PR where they appeared to be flaky. We can revisit later if we want to. If we need to use this script later and see failures we can just copy the message object from our unit tests and paste it over her.