Make password validation configurable

[Django149]

Right now, when creating a new user, the validate_password function is always called and enforces hardcoded rules for length, uppercase/lowercase letters, digits, and special characters.

It would be great to make this configurable, so people can adjust the password policy to fit their needs. This could be done in a simple way, like an ENABLE_PASSWORD_VALIDATION flag, or in a more flexible way, like a PASSWORD_POLICY config.

[SupeRoy100]

+1