More strict email address parsing (to match nodemailer)

[ignatiusm]

Resolves #909

From a slack discussion internally:

"Now looking at this code, I can't see how it possibly worked in the past!! As per the screenshot below, the HOSTNAME would include http:// which isn't a valid domain. My only idea was that maybe a library changed which enforced a more strict parsing.

I was hunting though our package.json and yarn.lock for libraries that might have changed, but our smtp is provided by Ethereal in dev and: checkout their fancy new updated website: https://ethereal.email/ and there is a new update to nodemailer from July 29th with changes that mean that it isn't silently dropping special characters anymore (see second screenshot).

Anyway, I think this is super interesting and am pleased it isn't anything to do with us. I guess the moral of the story is to not rely on special behaviour and try to provide the most specific data whereever possible"

Adds a test to verify the error, and a fix.

[iamtanuj18]

Fix looks clean and tests cover the paths that matter.

Small hypothetical worth noting: the if branch handles HOSTNAME with http/https prefix nicely via URL parsing. The else branch takes HOSTNAME as-is though, so if someone ever sets HOSTNAME as localhost:5173 (with port, no protocol prefix, via hand-editing .env), it'd still include the port in the from-address and probably fail. Unlikely since .env.example has the protocol and prod uses plain domains, but a defensive port-strip in the else would cover it.