Ensure uniqueness of email field when creating a user account.

[savacano28]

Description

Environment

OpenBAS - back

Reproducible Steps

Steps to create the smallest reproducible scenario:

1. Try create a user account with an email
2. Try again create a different user but with the same email but in different case (upper, camel, alter...)
3. Try login with email
4. Do you have a database problem? We're receiving two results instead of the expected one.

Expected Output

Just one result even if I try log in with my email in other case

Actual Output

Error database