feat: add privacy settings

[FreddyDevelop]

Description

Add two privacy settings, one that disables account enumeration protection (show_account_existence_hints) and one that only returns actual configured login methods of the user (only_show_actual_login_methods).

Although otherwise discussed these two settings also have an effect when email verification is disabled. And therefore the settings are added to a privacy section in the settings.

Implementation

Added some checks that if the settings are enabled an error might be returned e.g. the account or email does not exist.

Tests

Enable and disable email, email.use_for_authentication , username, password and check that errors are returned when user already exists or does not exists and that only authentication methods are returned that the user has configures.

MFA methods are not changed because they are only already returned when they are configured by the user.

Todos

We should add a page in the docs that describes these two settings.