fix: improve email validation using net/mail package

[sniperwolf]

📧 Improve email validation using net/mail instead of regex

Context

Currently, our email validation is using a regex pattern that doesn't fully support all valid email separators according to RFC 5322. This PR replaces it with Go's built-in net/mail.ParseAddress which properly handles all valid email characters.

Changes

• Removed regex-based validation
• Added net/mail package for proper RFC 5322 compliant validation
• Updated tests to cover more edge cases

Before

The current regex validation fails with valid email addresses containing special characters like +, {, }, ~, * etc.

Example of a valid email that was incorrectly rejected:

validemail+with_valid-separator{like}~these*[email protected] ❌

After

Using net/mail.ParseAddress, we now correctly validate emails containing all RFC 5322 compliant characters:

validemail+with_valid-separator{like}~these*[email protected] ✅

This change makes our email validation more robust and standards-compliant while actually simplifying the code by leveraging Go's standard library.

Would love to get this merged to improve our validation capabilities! Let me know if you'd like any changes or have questions. 🚀