Investigate strange behavior with single quotes in SMTP credentials

[sodic]

Version: 0.18.0
I discovered this while testing Open Saas in build mode (wasp-lang/open-saas#524).

SMTP credentials in waspc/todoApp look like this:

SMTP_HOST='smtp.mailgun.org'
SMTP_USERNAME='todoapp@mg.wasp.sh'
SMTP_PASSWORD='<redacted>'
SMTP_PORT=587

And I believe this works fine. But when I use the same credentials with Open Saas, it reports an error on signup and doesn't send an email:

To get it to work, I had to remove the single quotes.