[feat: backend] Validate a user's email address on registration

[therealjustinbiele]

Description

As a user signing up for our platform, I want to ensure that I provide a valid email address during registration, So that I can receive important notifications and access my account securely.

Acceptance Criteria

• When a user attempts to register, the system should verify that the provided email address follows the standard email format (e.g., "username@example.com").
• If the email address format is invalid, the registration process should not proceed, and an appropriate error message should be displayed to the user. Send a 400 BAD REQUEST error code as a response to the client
• The validation should check for common mistakes in email addresses, such as missing "@" symbol, invalid characters, or missing domain.
• The validation process should occur on the server-side to prevent bypassing by malicious users.
• The validation function should be reusable and easily maintainable.

[therealjustinbiele]

5 story points