NJWE-2584: implemented backend validation for valid email and domain

[denish-fearless]

NJWE-2584

TEST THIS ADDING MAILCHIMP KEYS TO YOUR BACKEND ENV
#MAILCHIMP
MAILCHIMP_API_KEY
MAILCHIMP_LIST_ID

This PR includes the full working for the signup form
https://fearless.jira.com/browse/NJWE-2654

[ChelseaKR]

Hey @denish-fearless,

CodeQL flagged a potential tainted format string issue in emailValidator.ts. The concern is that domain and rootDomain—which originate from user input—are being directly embedded in template literals inside console.error and console.log. This can introduce unintended format specifiers if the input contains special characters.

Suggested Fix:

Instead of using template literals, pass variables as separate arguments:

console.error("DNS error while resolving MX for domain:", domain, "-", err.message);
console.log("Valid MX records found for", domain, ":", addresses);

This ensures safe logging without unexpected behavior. Let me know if you have any questions! 🚀